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

As the second half of 2021 ended and Americans hoped for a summer of freedom from social distancing, a new threat was emerging due to lagging vaccination rates despite the widespread availability of 3 vaccines for COVID-19.

As the second half of 2021 ended and Americans hoped for a summer of freedom from social distancing, a new threat was emerging due to lagging vaccination rates despite the widespread availability of 3 vaccines for COVID-19.

By June, the more transmissible and contagious delta variant was taking root in the United States—primarily in unvaccinated populations—and leading to increased cases and hospitalizations.

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, and will be updated through the end of the year.

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 President 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

White House Chief Medical Advisor Anthony Fauci, MD, 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

President 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.