Firing the boosters

Now that the FDA and CDC have approved boosters for Covid-19, will it change the course of the pandemic? Possibly not--but pediatric vaccinations might.

Over the past two weeks, the Food and Drug Administration authorized, and the Centers for Disease Control and Prevention recommended, the broad and flexible use of “booster” vaccinations for a broad swath of the US population. Included in these recommendations was advice about heterologous boosting—aka “mix and match”—where one can start with one vaccine and move to a different vaccine as a booster.

I received my Pfizer booster after the FDA looked at the mix and match booster data. I was wondering if there would be any significant advantage to receiving a different booster. As a frontline worker, caring for Covid-19 patients on an almost daily basis, I had completed the Pfizer vaccine series in January, 2020. Based on what I had read, I did not perceive a significant advantage to receiving the Moderna or J&J/Janssen over repeating the Pfizer vaccine.

Data from Israel, and emerging data from elsewhere, show that the immune response to vaccination decays over time, with J&J/Janssen having the steepest rate of decay, followed by Pfizer and Moderna. The rate of decay for J&J/Janssen was so pronounced, that boosters have been recommended for anyone two months or more out from their vaccination. For Pfizer and Moderna vaccinations, boosters are recommended at six months after their second dose (or third dose, if it was given to an immunocompromised person). Vaccination after recovery from natural infection really boosts levels—so called “super immunity.”

Impact of prior SARS-CoV-2 infection on post-vaccination SARS-CoV-2 spike IgG antibodies in a longitudinal cohort of healthcare workers | medRxiv

Will the boosters make a difference? That depends. For the individuals receiving the boosters, it will likely enhance their ability to fend off severe disease. This is especially important for the folks at highest risk of adverse outcomes, such as hospitalizations or death. But for society as a whole, it is unclear that boosters will change the contour of the pandemic. Unvaccinated patients make up the vast majority of hospitalized patients, and the shortages of hospitals beds will continue with subsequent waves. While vaccinated people may still get Covid-19 and potentially transit infection, especially the delta variant currently dominating transmission (likely for not as long as the unvaccinated), we do not know yet how much boosters will affect transmission among the already vaccinated.

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Now attention has turned to pediatric vaccination, for the 5 to 11 year old cohort. It is estimated there are about 28 million children in this cohort—the vast majority swapping viruses in schools every day. While the risk of death is quite low—but not zero—we do know that children can transmit virus between themselves and to other family members. While influenza is not Covid-19, we classically see epidemics rage while school is in session, abate during winter holidays, then return when holidays are over. There is good reason we will see similar activity with Covid-19, especially in areas where school kids are not masked.

Some schools may choose to mandate vaccination for Covid-19, similar to mandates for other infectious diseases of childhood, such as measles. Other schools may wait for full FDA approval, which may not occur until next year. Based on the preliminary data, vaccination in children appears no more dangerous than vaccination in adults. While some may wonder about long term adverse effects of vaccine, these typically do not occur with most vaccines, and need to be balanced with the long term effects of Covid-19, both for the children themselves, and to their families. Over 140,000 children have lost a primary or secondary caregiver to Covid-19.

Most physicians I know are not hesitant to vaccinate their children—especially those of us who have seen the worst ravages of the disease.

For now, I am happy to be boosted.