Press "Enter" to skip to content

Dr. Petri dishes on COVID

Dr. William A. Petri, an immunologist at the University of Virginia School of Medicine, answers this week’s questions from readers 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.

1. Why did the COVID-19 vaccine fail to protect Colin Powell?

I think we are all saddened by the loss of such a great American, someone who served with distinction for the U.S. for his entire adult life and broke so many barriers to advancement for Blacks in the military and in public service. We will never know why the vaccine failed, but General Powell had many risk factors for more severe COVID-19: his age of 84, being a male and having multiple myeloma increased the risk of death from COVID-19 by several hundredfold. As far as breakthrough infections with the COVID-19 vaccines, we know that even with the delta variant surge that these remain uncommon (i.e., the vaccine remains highly but not completely effective), thus the recent recommendation for the Pfizer, and likely soon the Moderna and J&J vaccines to be boosted.

2. Should Type 1 diabetics who work in health care work directly with those with active COVID-19? I feel like it’s tempting fate, as they’re more at risk for complications/complicated cases of COVID-19, though not any more likely to get COVID-19 (if their diabetes is well- controlled). Thanks for answering all our COVID-19 questions!

First of all, thank you for being a health care worker. We all as a society owe so much to those who have and continue to provide care during the pandemic, including first responders to nurses, respiratory therapists and physicians. I hope that all of us will look back at 2020–2021 with gratitude to medical care and science for getting us through the pandemic. As far as the risk to health care workers, we are about twofold more likely to contract COVID-19, so your question is well-founded. I personally work with and care for patients with active COVID-19, although I am at somewhat increased risk being 65 years old. I do so in part because the use of PPE and vaccination (including booster) minimizes that risk. However I say that this is a personal decision on my own and your part, as it is key that each of us reach their own level of comfort.

3. Dr. Petri, with mask wearing, social distancing, antibacterial lotion on our hands after every visit to a store, doctor, etc, and then washing our hands when we get home, we haven’t had any colds since the start of the pandemic. But, are these practices weakening our immune systems since there are so few germs to combat? And, if so, is that dangerous? Thank you.

What an interesting question! The short answer is yes in the specific case of influenza. While I would not advise to stop wearing a mask and washing hands, I would recommend that everyone six months of age and older get the flu vaccine and do so soon, certainly before Thanksgiving. Our immunity to influenza may have waned since there was essentially no flu last year. In any case it is always a good idea to get the flu vaccine as it saves lives every year, maybe even more so for 2021.

4. My daughter got COVID back in May, so feels the antibodies she now has is better protection than the vaccine. But I say the antibodies diminish. Do we know when they diminish, and the rate? I ask in that my 91-year-old mom is coming for Thanksgiving. She will have had the vaccine and booster by then. Will my daughter put my mom at risk, or is it really that my daughter is the one at risk of COVID, and/or the variant? Right now she has no desire to get vaccinated. I am looking for any stronger facts to convince her otherwise. Thank you for taking my question.

I enjoy writing this column as the questions are so good, and I learn so much by reviewing what is known in order to answer them. I like your approach of using facts to convince others of the need for vaccination. The facts here are that vaccination provides about twofold added protection from reinfection in those who have recovered from COVID-19. This was shown in a study out of Kentucky that looked at 738 adults who had PCR-confirmed COVID-19 back in 2020. When the 246 patients who contracted a second COVID-19 infection in May-June 2021 were compared to 492 adults who did not (all of whom also had recovered in 2020 from COVID-19), vaccination reduced the risk of reinfection by 2.3-fold. It is great that your mother will have received the vaccine and booster by Thanksgiving. Having your daughter vaccinated would provide an added layer of security for your mother’s health for this reason. It is also important to remember that people can be infectious without having any symptoms, so while isolating at home is key when one has cold or flu symptoms, this does not entirely prevent transmission.

5. Is the reinfection rate for those who have had COVID-19 greater than the breakthrough infection rate for those who have been immunized?

It most likely is, although I cannot cite chapter and verse with hard data. What practically is important is that vaccination provides added protection to those who have recovered from COVID-19 (as we learned from the study from Kentucky above), and that the Pfizer booster shot provides added protection to those who are six months out from their primary series of vaccinations. So it behooves us all to be vaccinated, even if we had COVID-19 in the past, and to receive a booster at six months.

6. With the FDA saying that people who got the Moderna vaccine can still benefit from a booster, how will experts decide how much we should get? And when will it be ready?

Likely the FDA will approve the Moderna and J&J vaccine boosters later this month. FDA has a committee called the Vaccines and Related Biological Products Advisory Committee (VRBPAC) that met last week. VRBAC presented their conclusions to the full FDA that will rule on whether to grant emergency-use authorization for the use of boosters. The next level review will be with the Advisory Committee on Immunization Practices (ACIP). These are independent experts that are not FDA nor pharmaceutical employees. Assuming that the ACIP also recommends the boosters, then the final say-so will be from the CDC. A long-winded way of saying that the Moderna and J&J vaccine boosters will be ready at the end of this month in all likelihood. There is now data presented to FDA (although not yet peer-reviewed) that “mix or matched” boosters work well, so expect some word on that from the FDA, although the next most pressing thing on the FDA COVID-19 agenda is of course vaccination of 5- to 11-year-old children, the subject of an FDA meeting October 26th.

7. If we got our vaccinations months ago, how do we go about getting proof of vaccination now that there are so many reports of counterfeit vaccination cards? I want to start traveling again, and I don’t know what counts as legal certification.

As I write this I am flying back from England with my colleague Dr. Allie Donlan, where we had meetings on UVA’s COVID-19 immunotherapy program that is supported by the Manning Family Foundation. What we discovered on this journey is that the proof of vaccination is a bit different depending on what country you are visiting. To visit the UK one scans and uploads the vaccine card at the airline website prior to departure, and it is not needed to be shown again (for example to visit a restaurant or public place). One does need to get PCR tested two days after arrival in the UK, and no more than three days prior to return to the US, but thankfully this is all spelled out beforehand when you do the check-in paperwork. It does make sense to take a cell phone picture of the front and back of the vaccine card so that even if you misplace it you can pull it up on your phone.

8. If we get past the delta variant, can we have confidence that maybe COVID will be a thing of the past? Or are we going to have to keep getting boosters?

The genie is out of the bottle so to speak, and COVID-19 will be with us for some time to come. Projections are that by next spring if children are vaccinated and no new variants emerge, that COVID-19 will move from being pandemic to endemic, basically more like influenza. Additional good news is that since SARS-CoV-2 evolves much more slowly than, say, influenza, and because it does not cause latent infections like HIV, worldwide vaccination offers the promise of eventual eradication. I am seeing this right now at the WHO with polio, where I lead the Polio Research Committee. There has not been a child paralyzed with wild type polio since January! So we are on the cusp of global eradication of polio but this has taken three decades of concerted international effort.

9. Here’s what I would like to know that you did not provide further detail on last week: You state that we don’t know yet how high antibodies need to be to provide protection…. Is some scientific entity like the CDC currently even looking at this right now, running any kind of study between people who have acquired natural immunity and those who acquired immunity through vaccination?

Yes these studies are ongoing, but you are right to ask why we don’t already know the answer. In part we do, in that antibodies that neutralize the spike glycoprotein prevent infection, as evidenced by the fact that anti-spike monoclonal antibodies prevent and can even treat SARS-CoV-2 infection (work done in part right here at UVA). So it should be straightforward to measure these antibodies and determine if protective levels are present. However this is one of those “the devil is in the details” type things. The anti-spike IgG antibody tests detect both neutralizing and non-neutralizing antibody levels, so these tests do not directly measure the protection from infection conferred by the vaccine. In addition, each anti-spike antibody test that is on the market measures anti-spike antibody levels in a slightly different way and thus may not be directly comparable. Finally, vaccines protect not just with antibodies but via cell-mediated immunity which is much harder to measure. For most vaccines against infectious diseases, the FDA has determined antibody levels that are associated with vaccine-mediated protection, so this will happen. But I agree with you that it is frustrating today not to have a better handle on what level of anti-spike antibody correlates with protection.


Be First to Comment

    Leave a Reply

    Your email address will not be published. Required fields are marked *