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Q&A With Saad Omer: COVID-19 Vaccine Boosters

November 15, 2021
by Isabella Backman

On September 24, the first COVID-19 vaccine booster shots became available to Americans. These were for older people and those with other significant health risks who originally received the Pfizer-BioNTech vaccine. Data for Moderna and Johnson & Johnson vaccines took longer to compile, but in the following weeks, the US Food and Drug Administration (FDA) would also extend its Emergency Use Authorization to include a booster dose of these vaccines for certain groups.

But even as new variants of the virus begin to rise in prevalence, not everyone needs to worry about rolling up their sleeves just yet. We spoke with Saad B. Omer, MBBS, MPH, PhD, director of the Yale Institute for Global Health, to learn more about the science behind the boosters and the latest recommendations.

It seems that the narrative surrounding who needs a booster shot has been continually evolving. What is the current recommendation, and what are the data driving it?

OMER: The Biden administration had said that they anticipated based on some of the emerging data they evaluated that there could be—pending the decisions by the FDA and the CDC—a need for vaccine boosters, so therefore they would be making them available to Americans in late September. They always had the caveat—the FDA and CDC reviews. This got a little bit muddled, but that was the message to begin with. The administration wanted to make sure that the booster rollout didn’t come as a surprise to health care systems so that they had time to prepare.

Then, the FDA advisory committee went through their process, and they voted against a full booster for everyone. But, they voted in overwhelming favor of providing a booster for older individuals, 65 and older, and others who are at high risk of exposure.

The basis of these deliberations is the emerging data. Israel, for example, has been very prolific in producing good data. The bottom line is—it is very clear that these vaccines are highly effective, but there is some waning of protection against infection. How much of it is delta versus how much of it is waning immunity—I think it’s a bit of both. However, this decline in effectiveness is not there for severe disease in the general population. Finally, there may be some indication that this decline is indeed present to some extent—not a large extent—in older individuals who are over 65.



The current eligibility recommendations:

For individuals who initially received Moderna or Pfizer:

· 6 months-post second dose and

· At least 65 years-old or

· At least 18 years-old and

o Live in a long-term care setting

o Have an underlying medical condition or

o Live or work in high-risk setting

For individuals who initially received J&J:

· 2 months-post initial vaccination and

· At least 18 years old




Why do we need booster shots in the first place?

It often takes a couple of shots to mount the most adequate response, and a three-dose regimen is fairly common. Some types of Hepatitis A and Hepatitis B vaccines, for instance, require three doses. And inactivated vaccines usually require two to three doses, even for just the primary series. There’s also plenty of evidence that we need at least three mRNA vaccine doses for those who are immunocompromised. I think that’s a settled issue. The evidence has been around for a while and is the basis for why the CDC and others have recommended it.

Can you explain the research that has been done regarding the safety and efficacy of the COVID-19 boosters?

There are ongoing what we call post-market surveillance studies that include trials measuring efficacy in real life. There are also CDC and other surveillance systems that are evaluating safety as well on an ongoing basis by looking at adverse events in those who received boosters versus those who are unvaccinated. The current data indicate that boosters do help in terms of protecting against infection.

Are the booster shots the same as the initial doses?

The Pfizer booster and the second dose of the Johnson & Johnson vaccine are the same. For Moderna, the booster is half the dose of the original shot, but it works the same way.

How will side effects differ for the third round, if at all?

The data that has been presented by vaccine companies suggest that the third dose for mRNA vaccines does not have a higher frequency of most adverse events. Most data come from the Pfizer vaccine, but it’s likely to be similar for the Moderna vaccine. Overall, if anything, for many of these adverse side effects, the frequency is lower than the second dose.


If you received the Johnson & Johnson vaccine, is a booster recommended?

Yes, for certain groups. There are recent data that show that a second dose of Johnson and Johnson increases the vaccine’s effectiveness, especially in severe cases. These are very promising results. The data also evaluated immune responses at six months, and it showed that there was a much higher immune response at that time. So there may be a better immune response with a gap of six months, but even a two month gap between the two doses would impart very high protection against severe disease.

Some experts argue for referring to the next dose of the vaccine as the third dose in the series rather than a booster. Do you agree or disagree with this?

For immunocompromised individuals, I certainly believe in a three dose primary series. For others, it’s a little bit of a gray area on whether it’s a third dose or a true booster. But from a patient perspective, it really doesn’t matter. Whether you call it booster or a third dose, it’s going to work irrespective of what you call it.

The World Health Organization has urged countries to delay their push for boosters as many in low income countries still wait to receive their first dose. What are your thoughts on this call?

I think this is a reasonable call. They said “pause,” which was meant to highlight that there is a need for scaling up supply and production in low income countries. I personally think you could do both, but you have to have pretty substantial efforts to scale up the supply. The WHO focus was also on generalized boosters. And so for immunocompromised individuals, that wasn’t an issue. I think there is overall support for a focused booster for certain high-risk groups rather than a generalized booster, which is in line with what the FDA advisory panel recommended.

If an individual is both fully vaccinated and has had COVID-19, do they still need a booster?

Yes. There’s some evidence that may support a reduced number of doses in the future for those that have been infected, but for now the recommendation is still to get the booster.

If an individual has received the Johnson & Johnson vaccine, can they receive an mRNA booster?

While the CDC recommends that individuals who received the Johnson & Johnson vaccine get a second dose of the same vaccine, the recommendations also allow for receiving an mRNA vaccine.

Submitted by Robert Forman on November 15, 2021