On December 11, 2020, a SARS-CoV-2 (COVID-19) vaccine developed by Pfizer and BioNTech became the first to receive Emergency Use Authorization (EUA) from the U.S. Food and Drug Administration (FDA). Since then, two others (produced by Moderna and Johnson & Johnson) have also been granted EUA.

Pfizer's and Moderna's vaccines have many features in common: both utilize relatively new mRNA technology in a two-dose administration and both claim around 95% efficacy. In contrast, Johnson & Johnson has developed an adenovirus-based vaccine, provided in a single shot, that offers around 66% efficacy. In total, some 260 million doses of these three vaccines have been administered in the United States since December 2020, and just over one third of the population has been fully vaccinated. Though there is still a long way to go before the United States reaches herd immunity (if it ever does), promising data indicate that fully vaccinated people gain protection against different variants of COVID-19, are more resistant to developing asymptomatic infections, and may be less likely to spread COVID-19 to other people.

All U.S. residents over 16 have been eligible to be vaccinated since mid-April 2021, and the Johnson & Johnson shot will likely play a key role in the nationwide rollout: as a highly effective, single-dose vaccine, it is seen as a particularly attractive "one-and-done" candidate for accessing hard-to-reach communities (for example, isolated rural areas and poorer neighborhoods in major cities). However, since the Johnson & Johnson vaccine received authorization in late February 2021, its distribution in the United States has been met with a number of setbacks that have hampered its ability to help accelerate the national immunization effort.

In March 2021, up to 15 million doses of the Johnson & Johnson vaccine were contaminated by manufacturing mishaps at the Emergent Biosolutions plant in Baltimore, Maryland. Emergent, a multinational biopharmaceutical company, had partnered up with both Johnson & Johnson and AstraZeneca (whose vaccine is not yet authorized in the United States) to manufacture COVID-19 vaccines. It was discovered that workers at the plant had mixed up the two vaccines' ingredients, meaning millions of doses of the Johnson & Johnson vaccine had to be discarded. According to an FDA report released on April 21, 2021, Emergent agreed to "pause new production while it works with the FDA to resolve potential quality issues," meaning there could be significant delays in future shipments of the Johnson & Johnson vaccine from the Maryland production site.

By mid-April 2021, more than 6.8 million doses of the Johnson & Johnson vaccine had been administered to the American public. However, following reports of six different cases of a "rare and severe type of blood clot" in recipients of the vaccine, including one fatality, the FDA and the Centers for Disease Control and Prevention (CDC) jointly recommended a pause in the use of the vaccine while they took time to review the available data.

It is important to bear in mind that the Johnson & Johnson vaccine (like its Pfizer and Moderna counterparts) has not been approved by the FDA; rather, it has been granted Emergency Use Authorization. An EUA is "a mechanism to facilitate the availability and use of medical countermeasures, including vaccines, during public health emergencies" when "there are no adequate, approved, and available alternatives." An EUA can be revoked or terminated at any time if the FDA determines that the need for emergency authorization is no longer met. Following the successful rollout of its vaccine under EUA, Pfizer-BioNTech submitted a Biologics License Application (BLA) for full FDA approval of their two-shot regimen on May 7, 2021, which, if granted, could have important implications for vaccine mandates and marketing strategies. Moderna and Johnson & Johnson have not yet initiated BLAs (which require six months of post-immunization safety and efficacy data) for their vaccines.

Notably, even in light of the reports of blood clots in a small number of individuals, the FDA did not decide to revoke the Johnson & Johnson vaccine's EUA—instead, it recommended that states temporarily halt the use of the vaccine while the CDC's Advisory Committee on Immunization Practices (ACIP) convened to study the reported blood-clot cases. Following a 10-day pause, the ACIP (which is made up of medical and public health experts from across the country) and FDA released a joint statement on April 23, 2021 recommending that the use of the Johnson & Johnson vaccine be resumed, asserting that the vaccine's "known and potential benefits outweigh its known and potential risks." The FDA and ACIP further noted that the Johnson & Johnson Fact Sheet had been updated to explain that there is a very low risk of developing blood clots after receiving the shot, particularly in women under 50.

Now that the Johnson & Johnson vaccine is back in play, many hope that it will help meet the Biden administration's new goal of having 70% of American adults receive at least one shot by July 4, 2021. A further boost to the national vaccination effort came on May 10, 2021, when the FDA announced that the Pfizer vaccine EUA had been amended to permit administration to 12- to 15-year-olds.

Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

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