In the Race to Vaccinate, is One Shot Enough?

The Johnson and Johnson vaccine is quickly becoming the most quietly anticipated vaccine that is seeking FDA approval this month. What makes this vaccine different is the promise of being a single shot, without need for a booster. A single shot would mean freeing up the booster to inject into more arms and, in theory, increase vaccination availability by 200%.

But perhaps waiting for the Johnson and Johnson vaccine is not the only way to increase the number of vaccines available. Recent data has shown that the Pfizer/BioTech vaccine is somewhere between 50%-80% effective after a single dose.1 For perspective, last year's flu vaccine was estimated to be 45% effective.2 Britain has taken this data and run with it, recommending that as many people as possible get a single shot before allowing the administration of a second booster shot.3

This strategy relies heavily on a modified understanding of herd immunity, suggesting that more people with less immunity will slow the spread of COVID faster than fully vaccinating a few. Moreover, initial studies also show that those who receive a dose of the vaccine and then get sick with COVID get a less severe form of the disease, which could ultimately save lives of those who do become ill.1

Both Moderna and Pfizer/biotech initially set the suggested second dose at about 3 weeks from the initial dose. This timeline is ideal for finishing the series as quickly as safely possible. But there is limited data about how prolonging the time between doses changes its effectiveness. Still, Moderna, in part in response to the UK public health recommendation, has suggested that the second dose could be given up to a year later.3

The data needed to compare these strategies head to head will, by its nature, not be available for another year. Additionally, it is difficult to compare initial results in the UK and the US due to how drastically different their COVID responses have been up until this point. But as American states struggle with how to begin administering their allocated vaccinations, it is worth considering postponing boosters in favor of vaccinating everyone once.

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1. Schnirring, Lisa. “FDA documents show Pfizer COVID vaccine protects after 1 dose” CIDRAP News, University of Minnesota. Dec 08, 2020

2. “Interim Estimates of 2019–20 Seasonal Influenza Vaccine Effectiveness — United States, February 2020” Morbidity and Mortality Weekly, Centers for Disease Control and Prevention. February 21, 2020

3. Smont, Alistar. “Shots first, questions later: Britain's new COVID-19 vaccine rollout approach” Rueters. December 30th 2020.