Pfizer Plan for COVID Booster Shot Raises Safety Concerns
Opinion | On July 8, 2021, Pfizer, Inc. announced it was developing a booster dose for its experimental messenger RNA (mRNA) BNT162b2 biologic for COVID-19. It said that it had observed waning immunity among people who received the standard two-dose regimen of the product. The company said it planned to begin clinical studies of the third shot as early as August and would seek emergency use authorization (EUA) for the third doze from the U.S. Food and Drug Administration (FDA).1 2 In a written statement to CNN, Pfizer said:
As seen in real world data released from the Israel Ministry of Health, vaccine efficacy in preventing both infection and symptomatic disease has declined six months post-vaccination, although efficacy in preventing serious illnesses remains high. Additionally, during this period the Delta variant is becoming the dominant variant in Israel as well as many other countries. These findings are consistent with an ongoing analysis from the Companies’ Phase 3 study.1 2
Pfizer added:
While protection against severe disease remained high across the full six months, a decline in efficacy against symptomatic disease over time and the continued emergence of variants are expected. Based on the totality of the data they have to date, Pfizer and BioNTech believe that a third dose may be beneficial within 6 to 12 months following the second dose to maintain highest levels of protection.1 2
Pfizer’s proposal for a booster dose came on the heels of a finding by Israel’s Ministry of Health that BNT162b2 has proven to be only 64 percent effective in preventing symptomatic infections of COVID-19. The 64 percent rate is much lower than the 95 percent efficacy rate reported by Pfizer during the clinical trials for its product last year. This would, at least in part, explain why nearly half of the people in Israel being infected with coronavirus are those who have been fully vaccinated. The Pfizer/BioNTech shot is simply not providing the kind of high level of protection that was initially advertised.3 4
FDA, CDC and WHO Push Back on Booster Proposal
Within hours of the release of the Pfizer statement, the FDA and Centers for Disease Control and Prevention (CDC) issued a joint statement saying a third dose of the Pfizer/BioNTech biologic was not needed.1 5 6 According to the statement:
Americans who have been fully vaccinated do not need a booster shot at this time. FDA, CDC, and NIH are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary. This process takes into account laboratory data, clinical trial data, and cohort data–which can include data from specific pharmaceutical companies, but does not rely on those data exclusively. We continue to review any new data as it becomes available and will keep the public informed. We are prepared for booster doses if and when the science demonstrates that they are needed.ed.6
On July 11, Anthony Fauci, MD, White House medical adviser and director of the National Institute of Allergy and Infectious Diseases (NIAID), expressed support for the FDA/CDC position on a Pfizer/BioNTech booster.7 Dr. Fauci noted:
Given the data and the information we have, we do not need to give people a third shot, a boost, superimposed upon the two doses you get with the [Pfizer/BioNTech and Moderna/NIAID] mRNA [biologics] and the one dose you get with [Johnson & Johnson]. … There’s a lot of work going on to examine this in real time to see if we might need a boost. But right now, given the data that the CDC and the FDA has, they don’t feel that we need to tell people right now you need to be boosted.7
On July 12, representatives of Pfizer met in private with FDA and CDC representatives regarding the proposal for a booster shot. Pfizer shared preliminary data on its ongoing trials to develop a booster dose. The company characterized the meeting as “productive” and said that the participants agreed that “scientific data will dictate next steps.”8 9 “
It was an interesting meeting. They shared their data. There wasn’t anything resembling a decision,” Dr. Fauci said.8
The World Health Organization (WHO) has also come out in opposition to Pfizer’s call for a booster dose. “The priority now must be to vaccinate those who have received no doses and protection,” said WHO director-general Tedros Adhanom Ghebreyesus.
The chief scientist for the WHO, Soumya Swaminathan, MD said, “At this point, there is no scientific evidence to suggest that boosters are definitely needed,” adding that the WHO would decide on the need for booster shots “based on the science and data, not on individual companies declaring that the vaccines should now be administered as a booster dose.”10 11
CDC Says Booster May Pose Higher Risk of Serious Side Effects
One of the worries expressed by CDC officials regarding a third dose has to with safety—that the additional shot could come with greater risk. On July 13, Jay Butler, MD, the deputy director for infectious diseases at the CDC said:
The risk of some of the rare side effects that have been reported have been greater after the second dose, and even just the local reactions which are fairly common, are more common after the second doses as well. So we’re keenly interested in knowing whether or not a third dose may be associated with any higher risk of adverse reactions, particularly some of those more severe, although very rare, side effects.12
There is also some question about the safety of “mixing and matching” shots. For example, if a Pfizer/BioNTech booster shot was available, would it be safe to give it to people who had previously received Moderna/NIAID’s experimental mRNA-1273 biologic or Johnson & Johnson’s experimental Ad26.COV2.S vaccine for COVID-19? The CDC says that COVID-19 vaccines are not interchangeable.13
The CDC has stated clearly that if you receive a Pfizer/BioNTech or Moderna/NIAID biologic, “you should get the same product (or brand) for your second shot.” Logically, this recommendation would extend to a third shot, a booster.13
Dr. Swaminathan has warned that mixing and matching COVID-19 vaccines is a “dangerous trend.” She says, “We’re in a data-free, evidence-free zone as far as mix-and-match. There is limited data on mix-and-match,” adding… “Data from mix and match studies of different vaccines are awaited—immunogenicity and safety both need to be evaluated.”14
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Note: This commentary provides referenced information and perspective on a topic related to vaccine science, policy, law or ethics being discussed in public forums and by U.S. lawmakers. The websites of the U.S. Department of Health and Human Services (DHHS) provide information and perspective of federal agencies responsible for vaccine research, development, regulation and policymaking.
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