A nurse fills a syringe with COVID-19 vaccine. During a CATE mobile COVID-19 Vaccine clinic setup in ... [+]
I have had many questions about the sudden push for Covid vaccine boosters. One of my initial concerns about recommendations for a 3rd Covid vaccine injection—a booster—was whether the side effects would worsen. This was because the uncomfortable side effects from the 2nd injection were much worse than for the initial shot, especially for Moderna’s vaccine. Data from Israel have significantly allayed those concerns. Here’s what we know so far.
Israel is the leader in aggressively vaccinating its citizens, particularly since they have been overwhelmed by infections from the Delta variant. They have one of the highest rates per capita now. Israel also had data that suggested that the efficacy of the Pfizer vaccine had waned over time and, while still being 90% effective at preventing severe disease, it had dropped to 39% against infection.
Side effects
They, like others, began with vaccinating immunocompromised people. Almost a third had side effects, most commonly injection site pain. Other symptoms were fatigue (9%), muscle aches (4.3%), headache (4.3%), fever (1.4%), joint pain (2.1%), and vomiting or diarrhea (0.7%). Symptoms were short-lived, lasting 1-3 days.
Another report, from Israel’s HMO Clalit, comes from a survey of their members. They have already given a third dose of Pfizer/BioNTech vaccine to more than 240,000 people over 60-years old. They surveyed 4500; 88% of the respondents said they felt “similar or better” than how they had reacted to the second shot. Notably, ~0.4% said they suffered difficulty breathing, 0.3% complained of palpitations or chest pain, and 1% said they had sought medical care because of the side effects.
Clalit made a cryptic comment: “Some people who received boosters may have been suffering from significant side effects that precluded their participation in the survey.”
Since the vaccinations only occurred within the past month, any long-term side effects would not yet be apparent.
Further data from the Gertner Institute and KI Institute shows that the protection was 4x higher than after just two doses, measured from 10 days after the 3rd dose. The booster also had 5-6x greater protection against serious illness or hospitalization.
The initial side effects reported from a 3rd dose of the Pfizer/BioNTech vaccine are above. Something to remember is that the adverse effects were significantly lower with the Pfizer vaccine than with Moderna’s, and Israel used only Pfizer’s. Details of the differences in side effects are detailed in JAMA, with reports from the V-safe reporting system. Many of the reactions were reported 10-15% more often for Moderna. It will be important to warn patients that such unpleasant symptoms may well occur but generally last only 1-3 days. To boost vaccine uptake, it is also critically important, I believe, to give people paid sick leave.
Timing of boosters
One of my questions has been the timing of this third dose of vaccine.
Dr. Peter Hotez, Dean, National School of Tropical Medicine, has a nice graphic:
He notes that unpublished data suggests 8 months as a reasonable interval for boosting, given preliminary data on waning immunity. He also suspects that immunity after that will be long-lasting.
There are others concerned about the timing of boosters for the adult population (as opposed to immunocompromised adults, where there is general agreement). Helen Branswell has an excellent post on this: The decision “is being met with bafflement, concern, and even anger from a number of immunologists, vaccinologists, and people steeped in the normal way such decisions are made.”
One of the concerns was that the decision was made before the FDA even approved the Pfizer vaccine (which just happened today, 8/23) and before agreement from the Advisory Committee on Immunization Practices and CDC. This type of decision, outside standard procedures, breeds mistrust. Many of the specialists Branswell spoke with were not convinced that we would need a booster anytime soon.
Mix-n-Match
One of the questions I have gotten has been regarding mixing vaccine types. Since Moderna’s vaccine has seemed to be more effective vs. Delta infection (not necessarily severe disease), some have asked whether they should switch. Between the two mRNA vaccines, Pfizer and Moderna, Hotez recommends not changing.
The bigger question is what to recommend for people who got the Johnson and Johnson vaccine, and the experts have punted on this for now. Dr. Amesh Adalja, Senior Scholar, Johns Hopkins Center for Health Security, said, “There is some promise to mix and match strategies using mRNA vaccines and adenovirus vectored vaccines. This likely improves immunity…” but the data is not yet ready “to be able to turn this into a formal recommendation.”
Vaccine equity
Covid vaccinations by country income group
One of the major concerns about boosters is that of vaccine equity. The US, Europe, and Israel are busily giving (or preparing to give) boosters to their population when <2% of the people in low-income countries have received any vaccination.
The wealthy countries have been hoarding vaccines and now have an excess. In several US states, vaccine doses are being wasted and destroyed because of abysmal vaccine uptake. Adalja notes that one of the major problems is that of “government export restrictions.” Hotez shared a thought-provoking perspective with me: “Even if the US donated its entire stockpile of vaccines tomorrow, it would make very little impact. The focus around sharing existing doses will solve about 10% of the problem [and is not the solution]. We can and must produce 6 billion doses for the world now, while delta is circulating in Africa. Biden has already said what it’s committed to send out globally (is) 200 million Pfizer this year, 300 million next year. That number won’t change regardless of whether we boost or not.”
Distribution of people who have been vaccinated
This is where we stand today on boosters of the Covid vaccine. Besides the concern about equity, many people do not understand that if large populations remain unvaccinated, they will serve as breeding grounds for more resistant mutations that will again threaten us. It is in our self-interest to ensure that everyone in the world—including children—are vaccinated as quickly as possible. What will it take for wealthy countries to step up and do this?
