A Timeline of COVID-19 Vaccine Developments for the Second Half of 2021

December 2021 marks 1 year since the COVID-19 vaccine rollout began, and the current US death toll stands at over 800,000, compared with just 300,000 in December of 2020.

Although 2021 closes with a plentiful supply of COVID-19 vaccines and boosters, Americans continue to face challenges with the widespread Omicron variant and new testing hurdles.

Nearly 2 years into the pandemic, questions persist and new barriers arise.

To understand COVID-19 vaccine developments thus far, read the COVID-19 vaccine timeline from January 1 to June 30, 2021, or see the first COVID-19 timeline from 2020.

This is a timeline of COVID-19 vaccine developments from July 1, 2021.

July 6

Israel Data Show Dip in Pfizer Vaccine Efficacy

Government data reported from Israel show that the Pfizer/BioNTech vaccine is slightly less effective in preventing SARS-CoV-2, the virus that causes COVID-19, in recent weeks. The vaccine’s efficacy against illness was reported to drop from 94% to 64% based on data from June 6 through early July. Protection remained high against severe disease.

July 9

Pfizer to Pursue Booster Shots

Pfizer and BioNTech announce they will seek approval from the FDA for a booster of their mRNA COVID-19 vaccine, despite the agency saying a booster is not necessary at this time. With the delta variant making its way around the globe, the companies also said they will begin clinical trials of an updated 2-dose vaccine in August.

July 12

Addressing Full Vaccine Approvals

Anthony Fauci, MD, President Joe Biden's medical advisor, addresses concerns about COVID-19 vaccines being perceived as experimental and not fully tested due to their emergency use authorization status. According to Fauci, the lack of full approval is only a “technical issue” and data point to the high efficacy and safety of the vaccines worldwide.

FDA Issues J&J Warning

The FDA warns that the COVID-19 vaccine manufactured by Johnson & Johnson (J&J) can lead to an increased risk of Guillain-Barré syndrome. This rare condition occurs when the immune system damages nerve cells, causing muscle weakness and potential paralysis. Approximately 100 have been identified at this point.

July 13

Officials Say No Booster Shots Needed

Following a meeting with Pfizer, HHS officials say fully vaccinated individuals do not need a COVID-19 vaccine booster shot. At this point, no data have suggested a significant waning of vaccine efficacy or an increase in infections among those fully vaccinated.

July 14

Calls for Health Workers to Be Vaccinated

A statement from the Society for Healthcare Epidemiology of America calls on medical facilities to require workers to receive the COVID-19 vaccine, noting a sufficient rate of vaccination will not be achieved without a mandate. The statement also cites data showing rates of flu vaccinations increase when mandates for workers are in place.

July 21

Pfizer Vaccine Not as Effective Against Delta Variant

New research published in The New England Journal of Medicine shows the company’s vaccine is 88% effective against the highly transmissible delta variant compared with 95% to 100% efficacy seen in late-stage trials. Data also reveal a single dose of the vaccine or that from AstraZeneca is even less effective.

July 22

Vaccines for NYC Health Workers

Starting August 2, health workers in New York City will either need to be vaccinated or undergo weekly COVID-19 testing, according to a mandate put in place by Mayor Bill de Blasio. De Blasio hopes the move will help encourage vaccination uptake, while workers who refuse both options will be subjected to suspension without pay.

July 26

Vaccine Effects After Infection

Those previously infected with COVID-19 were more likely to have adverse health effects after their first dose of the Pfizer/BioNTech vaccine compared with those who were never infected, according to study results. However, symptom intensity was not different between the 2 groups and the most common symptoms included fatigue, headache and muscle pain.

Renewed Calls for Health Worker Vaccinations; VA Requirements

Fifty-seven medical groups endorse mandatory COVID-19 vaccines for all staff working in health and long-term care. The Department of Veterans Affairs is also the first federal agency to require the vaccine for its 115,000 health care workers. California and New York City now require the vaccine for municipal and state workers.

Moderna Expands Vaccine Study in Children

Following requests from federal regulators to expand its trial in children to better assess safety, Moderna announces it will do so and it is in talks with the FDA to recruit participants under the age of 12. It is not yet decided how many children will be added.

July 28

Fully Vaccinated Individuals Can Travel to England

England eases its travel restrictions for fully vaccinated Americans and Europeans. Beginning August 2, travelers will be permitted in the country and will no longer be required to quarantine upon arrival. However, test will still be administered after arrival and before departure.

July 29

Biden Calls for Federal Worker Vaccines

All civilian federal workers will need to either receive a COVID-19 vaccine or obey strict testing, social distancing, restricted travel, and mask requirements, according to the Biden administration. Those who chose not to get vaccinated will not risk being fired, and a mandate for all federal employees is not expected.

July 30

Concerns Mount as Vaccines Set to Expire

Officials are raising fears that COVID-19 vaccines may go to waste as expiration dates loom. As a result, the FDA announced a 6-week extension to the shelf life of the J&J single-dose vaccine, while 8 million unused doses were recently shipped out to states.

August 2

Florida Sets Infection, Hospitalization Records

Florida breaks its record for the greatest number of COVID-19 hospitalizations in the state, surpassing its total recorded more than a year and a half prior to the widespread availability of COVID-19 vaccines. The state also reported its most daily COVID-19 cases since the start of the pandemic.

August 3

70% of US Vaccinated

The country met Biden’s goal of having at least 70% of the population vaccinated with at least 1 dose of a COVID-19 vaccine 1 month after his initial deadline of July 4. At this point, the country is still 8.5 million people short of its previous goal to fully vaccinated 165 million individuals.

August 4

Majority of Older Americans Vaccinated

Kaiser Health News reports 90% of Americans aged 65 and older have received at least 1 dose of a COVID-19 vaccine, although rates vary between states. Pennsylvania, Hawaii, and Vermont have all vaccinated more than 99% of their seniors, while West Virginia ranks last with 78% of this population at least partially vaccinated.

August 5

Biden Plans to Have all Foreign Visitors Vaccinated

The Biden administration is formulating a plan to require all foreign visitors entering the United States to be fully vaccinated against COVID-19. At this point, the administration is not ready to immediately lift travel restrictions due to the prevalence of the highly transmissible delta variant.

August 6

CA Mandates Vaccine for Health Workers

California becomes the first state to require all health care workers receive a COVID-19 vaccination. All of the state’s 2.2 million health and long-term care workers have until September 30 to fulfill the mandate. California is experiencing its fastest increase in COVID-19 cases since the pandemic’s inception.

August 9

Fauci Predicts Vaccine Mandates Upon Full Approvals

Once the FDA fully authorizes any of the 3 currently available COVID-19 vaccines—now available under emergency use authorization (EUA)—Fauci predicts vaccine mandates will become increasingly common. Fauci says the approval could encourage schools, organizations, and hospitals to require student or worker proof of vaccination.

Vaccine Mandate Expected for Troops

Department of Defense (DOD) Secretary Lloyd Austin sends a memo recommending all DOD military and civilian personnel be vaccinated against COVID-19 and suggests a mandate will be issued at a later date. The Pentagon is not permitted to issue a vaccine mandate until a vaccine receives full approval or a presidential waiver is issued.

August 12

CDC Recommends Pregnant People Get Vaccinated

The CDC now urges all mothers-to-be to get vaccinated against COVID-19 in light of rising numbers of hospitalizations among unvaccinated expecting people. Expectant individuals with COVID-19 are at a higher risk of severe illness and pregnancy complications, including still births and miscarriages.

August 13

Booster Shot Endorsed for Immunocompromised

The CDC’s Advisory Committee on Immunization Practices (ACIP) votes 11-0 to recommend a 3rd dose of a Pfizer or Moderna mRNA vaccine for immunocompromised individuals, 1 day after the FDA approved the dose for people who have received organ transplants or have other conditions that have damaged their immune systems. There are around 7 million immunocompromised people in the United States.

August 16

Record COVID-19 Hospitalizations Among Children

The number of children hospitalized with COVID-19 reaches a record high, as those under the age of 12 are not eligible for vaccinations. This population makes up 2.4% of all hospitalizations in the United States and one-fifth of COVID-19 hospitalizations are in Florida.

August 18

Health Officials Announce Plan for Booster Shots in General Public

US health officials announce a plan for any American over the age 18 who received a COVID-19 vaccine to become eligible for a booster shot 8 months following their second dose of an mRNA vaccine, beginning on September 20, 2021. The plan is dependent upon additional reviews from the FDA and ACIP, and data is expected to determine when Johnson & Johnson vaccine recipients will need a booster.

CMS Mandates Vaccines for Nursing Homes

Medicaid- and Medicare-participating nursing homes must require staff to be vaccinated against COVID-19, CMS announces, or face losing federal funding. There are over 15,000 such facilities in the United States and as of August 8, only 62% of these staff have been vaccinated.

August 20

Booster Plan Backlash

The Biden administration’s plan to administer booster COVID-19 shots to the general public is met with backlash among individuals who feel more should be done to vaccinate the rest of the world’s populations before residents of wealthier countries are offered boosters. Others feel the decision may undercut trust in the vaccines already available.

Increases in Vaccination Rates

In the wake of the spread of delta, the United States saw a 31% week-over-week increase in the daily average of individuals becoming fully vaccinated, while the country administered 1 million vaccinations in 1 day for the first time in 7 weeks. Of doses administered, 562,000 were among people receiving their first dose.

August 23

Pfizer/BioNTech Vaccine Gains Full FDA Approval

The FDA grants full authorization to the Pfizer/BioNTech vaccine for individuals aged 16 and older, while some experts hope the news will convince vaccine holdouts to get immunized. Those aged 12 to 15 can still receive the vaccine under the initial EUA. In the wake of the announcement, New York City becomes the first region in the country to mandate vaccinations for all education staff.

Israel Data Supports Booster Shot Efficacy

Data from Israel show that among adults aged 60 and older who received a 3rd dose of an mRNA vaccine had significantly improved protection against infection and severe illness compared with those who received 2 shots. However, the study participants were particularly vulnerable to COVID-19.

August 24

Vaccine Mandates Announced

Following the FDA’s full approval of the Pfizer/BioNTech vaccine, several large organizations, including Disney, issues vaccination mandates for workers. President Biden has also urged private employers to issue similar mandates.

August 25

Delta’s Effect on Vaccines

CDC data show COVID-19 vaccines’ efficacy dropped from 90% to approximately 66% following the spread of the delta variant. Findings are based on the ongoing HEROES-RECOVER study of over 4000 health care and other frontline workers. Researchers emphasize results show the vaccines still protect people from contracting the virus.

Johnson & Johnson Releases Booster Shot Data

A booster dose of the J&J vaccine dramatically increases individuals’ levels of antibodies against COVID-19, according to a company report, while studies indicate higher levels of antibodies are linked with higher rates of protection. The lack of data regarding other parts of the immune system, like T cells, means there is not a precise estimate on the effectiveness of a booster shot against COVID-19.

August 26

Delta Air Lines to Charge Unvaccinated Employees

Beginning November 1, Delta Air Lines employees will face a $200 monthly increase on their health insurance premiums if they have not been vaccinated against COVID-19. The company self-insures its employees, and increased premiums for unvaccinated employees will be used to cover employees who are hospitalized with COVID-19.

Pentagon Requires Pfizer Vaccine

The Pentagon orders all active-duty service members to be vaccinated against COVID-19, but has not yet announced a deadline for the mandate to be completed. Around half of the US armed forces are already fully vaccinated, according to the military.

September 7

Pfizer Plans to Roll Out Boosters Starting September 20

Fauci says wide distribution of Pfizer’s booster shot against COVID-19 is expected to begin the week of September 20, although the plan still needs approval from public health officials. Due to a lack of data, Fauci recommends against Moderna recipients receiving a Pfizer booster dose.

Bristol Meyers Squibb Requires Vaccination

The pharmaceutical giant is requiring all of its employees in the mainland United States and Puerto Rico to receive a vaccination against COVID-19 by November 1, Seeking Alpha reports. The majority of its employees (85%) are fully vaccinated, while in August, both Pfizer and Moderna mandated all their employees get vaccinated.

September 9

Biden Announces Vaccine Mandates for Most Firms

Biden announces all companies with over 100 employees must mandate COVID-19 vaccinations or have workers undergo weekly testing; those who do not comply will face up to $14,000 in fines per violation. Companies would also have to give workers paid time off to receive vaccines and to recover from any adverse effects. All health care workers at facilities that receive Medicare or Medicaid funding will be required to get vaccinated, as will federal contractors.

September 10

Los Angeles Schools Mandate Vaccines

The city’s board of education approved a measure requiring all children aged 12 and older to be vaccinated against COVID-19. The move marks the first such mandate among one of the nation’s largest school systems, which currently tests all students and employees for COVID-19 each week.

September 13

Unvaccinated People 11 Times More Likely to Die

CDC data show unvaccinated individuals are 11 times more likely to die than their fully vaccinated counterparts. A study of 600,000 Americans also found fully vaccinated individuals are 5 times less likely to be infected with COVID-19 and 10 times less likely to require hospitalization.

September 14

Expert Review: Boosters Not Needed Among General Public

Published in The Lancet, an expert review of scientific evidence concluded booster doses of COVID-19 vaccines are not needed for the general public at this time, as vaccines in the United States continue to provide highly effective protection against severe disease and hospitalization caused by the delta variant.

September 15

Hospitalizations Among Unvaccinated Cost Billions

Data from the Peterson-KFF Health System Tracker showed that between June and August 2021, preventable COVID-19 hospitalizations among the unvaccinated cost over $5 billion. In June, there were approximately 32,000 preventable hospitalizations; in July, 68,000; and in August, 187,000—for a total of 287,000 in 3 months.

September 17

FDA Committee Votes Against Boosters for General Public

An advisory committee voted against boosters for those in the United States aged 16 and older but endorsed a measure to provide boosters to people 65 years and older or who are at a high risk of severe COVID-19. The FDA does not need to follow this committee’s recommendation, but usually does. Talks will continue regarding booster distributions for frontline workers, teachers, and others at a higher risk of contracting and spreading COVID-19.

September 20

Pfizer Says Vaccine Is Safe, Effective in Children

Pfizer and BioNTech announce in a press release that a new formulation of the companies’ vaccine is safe for use in children aged 5 to 11 years. Data have not yet been released or peer reviewed and are based on a clinical trial assessing the efficacy of one-third of the approved adult dose.

Available COVID-19 Vaccines Remain Effective

Updated CDC data underscore the continued efficacy of all 3 COVID-19 vaccines available in the United States. Although some variation was reported in levels of protection, authors concluded all 3 provide substantial protection against hospitalization.

September 21

J&J Announce Efficacy of 2-Dose Vaccine

A 2-dose version of J&J's COVID-19 vaccine has comparable efficacy to the 2-dose regimens from Pfizer/BioNTech and Moderna. J&J released data that the 2-dose vaccine provided 94% protection against symptomatic infection. The company had 3 studies evaluating the vaccine and together, they showed the protection was boosted with an extra shot. One trial gave the 2 doses 56 days apart and another gave the booster shot 6 months or later.

September 22

US to Double COVID-19 World Donations

Biden plans to increase the country’s purchase of Pfizer COVID-19 vaccines to 1 billion doses to donate globally, raising the United States’ commitment to more than 1.1 billion doses through 2022. The president plans to vaccinate 70% of the global population by next year.

FDA Authorizes Pfizer Booster

Individuals 65 years and older, as well as younger adults at risk of having severe COVID-19 or whose jobs expose them to the virus more frequently, are now eligible to receive Pfizer booster doses. Individuals who originally received a Pfizer vaccine can get their third dose 6 months after their second.

September 23

ACIP, CDC Director Support Boosters

The CDC’s Advisory Committee on Immunization Practices (ACIP) voted 15-0 in favor of Americans 65 years and older and those in long-term care facilities receiving a booster shot. In addition, CDC Director Rochelle P. Walensky, MD, MPH, said that frontline health care workers aged 18 to 64 years may get boosters, overruling ACIP’s 9-6 vote against that recommendation.

September 29

Adverse Effects of Boosters Similar to Second Dose

Individuals who received a third dose of either a Pfizer or a Moderna vaccine reported similar adverse effects to those reported after a second dose, CDC data show. The findings are based on results of a survey conducted among 12,500 people and no unexpected patterns of adverse reactions were observed.

September 30

CDC: Pregnant Women Should Get Vaccinated

The CDC releases data showing vaccination of COVID-19 does not increase risk of miscarriage, issuing its strongest recommendation yet for pregnant individuals to get vaccinated—at this point only 31% of pregnant woman are vaccinated in the United States.

October 5

Sustained Efficacy of Pfizer Vaccine

Despite findings that show the vaccine wanes in efficacy against COVID-19 infection over time, new data reveal the Pfizer vaccine remains 90% effective in protecting against hospitalization and death from COVID-19, up to 6 months after individuals receive their second dose.

October 8

Moderna Pressured to Ramp Up Production

The Biden administration is pushing Moderna to increase its production of COVID-19 vaccines to distribute globally in 2022. Meanwhile, low- and middle-income countries in the COVAX program report being left in the dark as to when shipments will arrive.

October 13

Biden’s Vaccine Mandate Moves Forward

The Occupational Safety and Health Administration submits the initial text of an emergency vaccine rule to the Office of Management and Budget (OMB) for review, paving the way for Biden’s vaccine mandate for large businesses. The rule will go into effect after the OMB finishes its review and it is published in the federal register.

October 15

US to Open to Vaccinated Travelers

Beginning November 8, vaccinated foreign travelers will be allowed in the United States, while those traveling by air will have to show proof of vaccination and a negative COVID-19 test taken within 3 days before boarding the plane. Land and ferry travelers will need to show proof of vaccination but will not be required to get tested.

October 20

Mixing, Matching of Boosters Approved

Individuals eligible for a booster shot are able to receive one from a different company than that which provided their original dose, the FDA said. The move comes after the FDA approved booster doses from both Moderna and Johnson & Johnson. All recipients of the Johnson & Johnson 1-dose vaccine are now eligible for a booster dose from any of the 3 brands.

October 21

Pfizer Booster Lowers Risk of Infection Compared With Placebo

Data show the Pfizer booster vaccine resulted a significant 95.6% lower risk of infection than fully vaccinated individuals who received placebo. The study included 10,000 people 16 years and older.

October 25

Moderna Dose Effective in Children

Moderna’s COVID-19 vaccine formulation for children is safe and produces a powerful immune response among those aged 6 to 11 years, new data show. The company plans to submit results soon to the FDA and other regulatory agencies around the globe.

October 26

FDA Panel Supports Pfizer Vaccine for Children

An FDA advisory panel votes in favor of authorizing Pfizer’s COVID-19 vaccine for children aged 5 to 11 years. The Vaccines and Related Biological Products Advisory Committee votes 17-0, with 1 abstention, that 2 10-mcg doses of the Pfizer vaccine should be granted emergency use authorization for this age group.

October 29

FDA Authorizes Pfizer Vaccine for Children

The FDA issues an emergency use authorization for the Pfizer vaccine for those aged 5 to 11, although the vaccine still needs to be recommended by the CDC before it becomes widely available, STAT News reports.

November 1

FDA Investigates Moderna Vaccine Adverse Effect

The FDA announces it will need more time to decide whether to approve Moderna’s COVID-19 vaccine in children aged 12 to 17 years due to reports of a rare adverse effect in recipients. According to Moderna, of the more than 1.5 million adolescents who received its vaccine, no increased risk of myocarditis was found.

Global COVID-19 Deaths Top 5 Million

More than 5 million people have now died due to COVID-19 nearly 2 years into the pandemic, with upper-middle and high-income countries accounting for almost half of all deaths. At this point, confirmed COVID-19 cases in the United States are on the decline.

November 2

CDC Panel Meets on Vaccines for Children

A CDC panel meets to decide to recommend Pfizer/BioNTech or Moderna vaccine for children aged 5 to 11 years with the Biden administration already preparing to deliver millions of the shots to this population. The doses would be one-third of those given to adults.

November 3

CDC Director Recommends Pediatric Vaccine

Rochelle P. Walensky, MD, MPH, endorses the CDC Advisory Committee on Immunization Practices’ recommendation that children aged 5 to 11 years receive a Pfizer-BioNTech pediatric COVID-19 vaccine, expanding eligibility to approximately 28 million children.

Unvaccinated Employees May Be Refused Death Benefits

Several employers announce families of unvaccinated individuals who die of COVID-19 may not receive death benefits. With the wide availability of the safe and effective vaccines, more employers are expected to implement similar rules.

November 5

Pushback on Vaccine Mandate

After President Joe Biden released a more detailed plan for large private employers to vaccinate their workers, several Republican state officials expressed their objection to the measure and are working to rebuke it. At least 2 conservative groups filed lawsuits against implementation.

November 8

Biden Urges Court to Allow Employer Vaccine Mandate

In the wake of several lawsuits, the Biden administration issues a 28-page filing to the United States Court of Appeals for the Fifth Circuit arguing the federal government has all the necessary power to require large employers to mandate COVID-19 vaccination or weekly testing and mask wearing in their workforce.

November 9

Pfizer To Ask for Booster EUA for All Adults

It’s reported Pfizer is planning to ask the FDA for an EUA broadening the scope of its booster shot for all US adults aged 18 and older. At this point, the booster is only available to those age 65 and older or those aged 18 to 64 who are at high risk of severe COVID-19 or work in areas that increase risk.

November 11

Moderna, NIH Clash on Vaccine Patent

NIH is continuing to fight for 3 of its scientists to be given credit on a patent application for their part in developing Moderna’s COVID-19 vaccine; the vaccine resulted from a years-long collaborative effort between the 2 organizations. If researchers prevail in the dispute, the government can license the manufacture of the vaccine, potentially providing access to poorer nations.

November 13

Appeals Court Affirms Hold on Employer Vaccine Mandate

A 3-member panel of the US Court of Appeals in the 5th Circuit affirms its ruling to keep President Biden’s vaccine mandate for employers on hold. The panel said the mandate was overbroad and did not account for differences in workplaces and employees.

November 18

Moderna Seeks EUA for Booster in All Adults

Moderna asks for an expansion of the company’s EUA for its booster shot, which is currently authorized for those 65 years or older and adults at high risk for severe COVID-19 due to underlying conditions or their living or work environments.

November 19

FDA Approves COVID-19 Boosters for All Adults

Booster shots are now available for all US adults over the age of 18 if they are more than 6 months out from completing their primary vaccination series of mRNA vaccines. Any individual who received the 1-dose Johnson & Johnson vaccine could already get a booster.

Midwest Sees COVID-19 Spike Among Unvaccinated

The upper Midwest is seeing the largest surge in infections as the country’s average daily cases increase by 35%. In the last week alone in Minnesota, COVID-19 cases rose 47% and hospital admissions rose 24%, with the largest increase seen among those aged 30 to 49 years.

November 22

Global Vaccine Disparities

Low-and middle-income countries where some vaccine clinical trials were hosted received disproportionately less doses than their high-income counterparts, JAMA Network Open data show. WHO Director-General Tedros Adhanom Ghebreyesus has expressed it is unacceptable vaccine manufacturers have overwhelmingly supplied rich countries at the highest prices.

Stillbirth Risk in Pregnant Women With COVID-19

New data show stillbirth risk is notably higher in women with COVID-19, particularly those infected with the Delta variant, while obstetricians are finding notable differences in how much oxygen fetuses can absorb depending on whether their mothers have been diagnosed with COVID-19.

November 23

Long-Term Efficacy of Pediatric Pfizer Vaccine

Data from Pfizer/BioNTech show the companies’ COVID-19 vaccine was 100% effective in preventing infections among kids aged 12 to 15 years. Efficacy was measured from 7 days to 4 months after administration of the second dose of the vaccine in over 2000 participants.

November 25

South Africa Announces Omicron Variant

Scientists in South Africa announce they have found a new COVID-19 variant of concern, The New York Times reports. In response, several countries close their borders to international travelers from the region. The variant’s mutations are described as a “big jump in evolution” by one scientist.

November 30

CDC Endorses Boosters for All Adults

The CDC expands its recommendation on COVID-19 booster shots for all adults aged 18 and older in the wake of the Omicron variant. In a technical brief the World Health Organization says the global risk from the Omicron variant is very high based on early evidence.

10 States Suspend Mandates for Health Workers

A federal judge temporarily blocks COVID-19 vaccine mandates for health workers in 10 states that had challenged the law. The preliminary injection rules that CMS had no clear authority from Congress to enact the mandate for participating providers in Medicare and Medicaid.

December 2

First US Omicron Case

A vaccinated traveler who returned to California after a trip to South Africa marks the first confirmed case of the Omicron variant in the United States. The person experienced mild symptoms before testing positive and was not vaccinated long enough to receive a booster.

Federal Judge Blocks Vaccine Mandate for Health Care Workers

A federal judge issues a preliminary injunction to halt the start of President Joe Biden’s national vaccine mandate for health care workers, which was set to begin December 6. The decision expands the separate order issued on November 30.

Biden Response to Omicron Variant

The president announces a new strategy to combat the Omicron variant which includes expanding vaccinations to the remaining unvaccinated Americans, CNN reports. The plan also focuses in increasing booster uptake among vaccinated Americans and requiring insurance companies to pay for at-home COVID-19 tests.

December 6

Disproportionate Vaccine Distribution

A new study indicates Africa has a minimal likelihood of overcoming the COVID-19 pandemic unless 70% of its population is vaccinated by the end of 2022. Only 5 of Africa's 54 nations are on track to fully vaccinate 40% of their population by this year’s end, while about 70% of countries in the G7 group have already met the full vaccination target.

Omicron Linked With Less Severe Disease

Preliminary data out of South Africa show the Omicron variant may lead to less severe cases of COVID-19 and is not leading to a significant rise in hospitalizations in the country. Scientists still need more information to definitively assess Omicron’s severity compared with the dominant Delta variant.

December 7

Mixing COVID-19 Doses Increases Immune Response

Individuals who received a first dose of AstraZeneca or Pfizer/BioNTech COVID-19 vaccines were shown to exhibit higher antibodies and T-cell responses when given the Moderna vaccine 9 weeks later, new data show. No safety concerns were cited, but study limitations included its older adult and primarily White cohort.

December 8

Pfizer Shot Offers Some Omicron Protection

Although data from South Africa indicate the new variant dulls the efficacy of Pfizer’s vaccine, people who have received a booster shot may be better protected. Study findings do not offer a full picture of how vaccines work to prevent Omicron-related hospitalizations or death.

December 9

Pfizer: Omicron May Warrant 4th Dose

Pfizer executives say the new Omicron variant could increase the likelihood people will need a fourth dose of a vaccine earlier than expected. Previously the company’s CEO projected a fourth dose of a COVID-19 vaccine may be needed 12 months after a person receives their third dose.

December 10

Booster Access Expanded

The FDA endorses Pfizer/BioNtech booster shots for those aged 16 and 17. The CDC subsequently says these teens should receive the doses as soon as 6 months have passed following their last dose. The booster is identical to the previous 2 in the Pfizer regimen.

December 13

Pfizer Efficacy Against Omicron

Data from South Africa show the Pfizer 2-dose regimen may only have a 22.5% efficacy against symptomatic infection with the Omicron variant, but can still prevent severe disease. Those who receive a booster may be better protected.

December 14

1 Year Since Vaccine Rollout Began

It’s been 1 year since the shipment of COVID-19 vaccines across the country. Currently, the nation’s death toll stands at around 800,000 compared with 300,000 this time last December. Unvaccinated Americans have a 14 times higher risk of dying of COVID-19 compared with the vaccinated.

All 3 Vaccines Safe in Patients With MS

A study shows all 3 vaccine types that protect against COVID-19—inactivated virus vaccines, adenovirus vector vaccines, and messenger RNA vaccines— are safe for patients with multiple sclerosis (MS) to receive. Researchers recommend those with MS receive a COVID-19 vaccine.

December 15

Omicron Wave Expected in January

As the Omicron variant spreads rapidly across the country, US health officials warn of a surge in cases in January 2022. CDC data show prevalence of Omicron multiplied by 7 in a single week while Delta cases are still increasing.

December 16

Moderna Vaccine Efficacy Reduced

Study results show 2 doses of the Moderna vaccine may be about 50 times less effective at neutralizing the Omicron variant compared with the original variant of COVID-19, while those who received a third dose of Moderna showed antibodies highly effective at blocking the Omicron variant, which had similar effectiveness at blocking the Delta variant.

Court Revives Health Care Worker Vaccine Mandate

A federal appeals court revives Biden’s COVID-19 vaccine mandate for health care workers employed by federally funded health facilities, a rare win for the President’s pandemic strategy. According to the mandate, health facilities must get their workers vaccinated or risk losing federal funding.

December 17

J&J Blood Clot Concerns

The CDC recommends individuals receive Pfizer/BioNTech or Moderna vaccines over the J&J vaccine due to concerns of rare blood clots. Cases of rare and potentially fatal thrombosis with thrombocytopenia syndrome (TTS) and cerebral venous sinus thrombosis occur in about 1 in every 100,000 cases of at-risk women aged 30 to 49 years.

Antibodies Seen in Those With Blood Cancer Who Receive 3rd Dose

A registry study finds a third shot of an mRNA vaccine could be crucial for some patients with blood cancers, as these patients exhibited COVID-19 antibodies for the first time. Some patients included in the study even showed antibody levels on par with healthy adults after their third dose.

December 20

US Vaccine Rates Overestimated

The CDC has overcounted how many Americans are at least partly vaccinated against COVID-19, reducing the share of people 65 years and older with at least one shot from 99.9% to 95%. The number of raw shot totals has not changed as the agency acknowledged it counted too many shots as first doses when they were instead second doses or booster shots. However, the miscount resulted in an underestimation of those fully vaccinated and completely unvaccinated.

Moderna to Develop Omicron-Specific Booster

Despite positive preliminary data showing the company’s booster shot helps protect against the Omicron variant, Moderna announces it plans to develop an Omicron-specific booster dose. The current FDA-approved booster was found to increase neutralizing antibody levels against omicron 37-fold compared with pre-boost levels.

December 21

Free At-Home COVID-19 Tests

In an effort to help stem the spread of the Omicron variant, the Biden administration announces it will ship 500 million free rapid COVID-19 tests to Americans in January 2022. Currently, the Omicron variant accounts for 73% of new US COVID-19 cases.

December 22

2021 On Track to Surpass 2020 Death Toll

Although it will still be weeks until total numbers are counted, data indicate 2021’s death toll will surpass that of 2020 by around 15,000. Even though 2020 was the deadliest year on-record in the nation’s history, new figures show the toll was worse than what was previously reported. Compared with 2019, life expectancy in 2020 fell by 1.8 years.

December 23

Omicron May Carry Lower Hospitalization Risk

Data out of the United Kingdom indicate the Omicron variant may be milder than the Delta variant. However, scientists cautioned any reductions in severity need to be weighed against the fact that the new variant spreads much faster than the Delta variant. A significant number of Omicron infections could also overwhelm hospitals.

Cities Require Proof of Vaccination

In January, Boston and Chicago will begin requiring proof of vaccination to enter indoor spaces, including gyms, restaurants, and entertainment venues. New York City and Los Angeles have already implemented similar measures.