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Dr. Petri talks booster shots, Aaron Rodgers, and more

Dr. William A. Petri, an immunologist at the University of Virginia School of Medicine, answers this week’s reader questions on COVID-19. Dr. Petri will keep dishing on COVID-19 and answering your questions each week in The Daily Progress for as long as you have questions. Send them to Editor Lynne Anderson at:, and she will forward them to Dr. Petri.

Was Aaron Rogers correct in saying he was immunized against COVID-19 by receiving monoclonal antibody treatment?

Maybe! With the support of 24 volunteers from Charlottesville (thanks to each of you reading this!) we at UVA were part of the study demonstrating that the anti-spike monoclonal antibodies casirivimab and imdevimab are 80% effective at one month in preventing household transmission of COVID-19 (published yesterday in the New England Journal of Medicine). Well, we continued to test these volunteers for COVID-19 infection over the last year, thanks to Igor Shumilin, the clinical research coordinator for our study. The wonderful result is that the antibodies provide 80% protection for as long as eight months after injection! This was announced in a press release this week from Regeneron Pharmaceuticals. So if these are the antibodies that Aaron Rogers received then he may in fact have been “passively” immunized from COVID-19. However, these antibodies do not replace vaccines, as eventually the antibodies wear off, whereas the vaccine provides protection well beyond eight months.

Seeing as how having COVID gives you natural immunity, wouldn’t that plus having the vaccine negate the necessity for a booster?

A few things going on here. First, it might not be the number of vaccine shots but rather the amount of time that has passed since you were vaccinated that is primarily important (since we know that Pfizer vaccine-induced immunity waned in the 6 months following the primary vaccination). Second, the Delta variant is harder to protect against with the current vaccines than the Alpha and Wuhan strain. Third, if you had a breakthrough infection after being vaccinated, then you likely had an inadequate response and will benefit from a booster.

If I received the Johnson & Johnson vaccine, which is the better booster to ask for – Moderna or Pfizer? And do I get a choice?

Great question. Actually all three vaccines as boosters (including J&J) work equally well, so there is no way to go wrong. This is based on a study conducted at the University of Maryland where every possible combination (9 total) of primary vaccine series and boosters was tested. So expect a 20-fold increase in the protective levels of antibodies, and protection from infection, regardless of which booster you receive. Also please note that you, and everyone who received the J&J vaccine, is eligible for a booster two months after completing the initial single dose vaccination. I would call your health care provider or vaccination clinic or pharmacy to see what boosters that they have available, and check to see if they allow you to choose. But again, no way to go wrong here.

What side effects should I look for in my younger child?

The side effects are the same as adults have experienced, and are generally mild, not unlike other childhood vaccines. Expect a sore arm in most children, and less commonly a day of fatigue or flu-like illness.

Can I go into grocery stores, movie theaters and other enclosed public places if I have been boosted?

Yes. Being vaccinated and now boosted is a liberating experience! I still wear a mask indoors in public spaces (making an exception in restaurants while eating) but the risk of contracting COVID-19 is greatly diminished by all three vaccines. And additional good news is that the surge of infections due to the Delta variant is ebbing, with half the number of new cases today compared to the peak at the beginning of September. So vaccination plus less transmission of Delta is putting us in a good place as Thanksgiving approaches, and I am looking forward to the family time over the holidays that I sorely missed last year.

How long will we need to keep getting boosted?

No one knows for sure, but it is unlikely that it will be an every-year thing the way that the flu shot is. This is because the SARS-CoV-2 virus changes or mutates much, much slower than influenza. This virus actually has a proof reader much like a spell checker that limits mutations. So the COVID-19 vaccine will not need to be redesigned each year the way the flu shot is. An unknown is how long the immune system will remember the vaccination, which only time will tell. Should immunity wane this will be detected by the CDC through active surveillance of the most vulnerable populations such as residents in long-term care. That would be a signal that another booster is needed.

When will non-prioritized people be able to get a booster? (For example, I am a 25 year old with no preexisiting conditions, and someone who doesn’t work in health care.)

Actually, you may already be eligible! High-risk occupations that are eligible for boosters six months after receiving the Pfizer or Moderna vaccine include those with an occupational exposure; including teachers, retail, transit manufacturing and agricultural workers. And of course this group includes everyone 65-years-old and older, 18-years-old and older with an underlying medical condition, and first responders and health care providers. Remember too that everyone who is two months out from receiving the J&J vaccine is eligible for a booster. For everyone else, the CDC is actively monitoring vaccine effectiveness in the currently excluded groups, and if the vaccine becomes less protective the CDC will move quickly to widen their recommendations for who should be boosted.


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