Do COVID-19 Vaccines Reduce Transmission Times? A Closer Look

A letter to the Editor published in the December 23rd, 2021 issue of the New England Journal of Medicine, titled “Viral Dynamics of SARS-CoV-2 Variants in Vaccinated and Unvaccinated Persons” led many media outlets to write articles with sensational headlines that COVID-19 vaccines reduce transmission in breakthrough cases. USA today headline read: “NBA study finds vaccinated people with breakthrough coronavirus infections less likely to infect others”. That is such an oxymoron! Viral infection is being transmitted from one vaccinated individual to another, and yet it is a case of glass half-full and that vaccines are effective in reducing transmission!

Now let’s examine the data presented in this NEJM letter with my reviewer hat on and examine whether the data justifies the conclusions.

The authors investigate two hypotheses: First, when an individual gets infected with the delta variant, is the viral load is higher than in those people infected with other variants of SARS-CoV-2? Second, vaccinated people when infected with SARS-CoV-2 may clear the infection more quickly than unvaccinated people.

To test their hypotheses, the authors obtained 19,941 SARS-CoV-2 viral samples from 173 individuals enrolled in the occupational health program of the National Basketball Association (NBA) between November 28, 2020, and August 11, 2021. This longitudinal set of data was analyzed prospectively.