20 January 2021

The New York Times: “Underselling the Vaccine”

  • If anything, the 95 percent number understates the effectiveness, because it counts anyone who came down with a mild case of Covid-19 as a failure. But turning Covid into a typical flu — as the vaccines evidently did for most of the remaining 5 percent — is actually a success. Of the 32,000 people who received the Moderna or Pfizer vaccine in a research trial, do you want to guess how many contracted a severe Covid case? One.

  • Although no rigorous study has yet analyzed whether vaccinated people can spread the virus, it would be surprising if they did. If there is an example of a vaccine in widespread clinical use that has this selective effect — prevents disease but not infection — I can’t think of one! Dr. Paul Sax of Harvard has written in The New England Journal of Medicine. (And, no, exclamation points are not common in medical journals.) On Twitter, Dr. Monica Gandhi of the University of California, San Francisco, argued: Please be assured that YOU ARE SAFE after vaccine from what matters — disease and spreading.

David Leonhardt

There are several examples of vaccines that to not provide “sterilizing immunity” – for example the two polio vaccines confer different types of immunity, OPV sterilizing and IPV non-sterilizing – but nevertheless vaccines can be very effective in substantially reducing disease spread and putting a stop to epidemics. In a vaccinated person, the immune system recognizes the pathogen from the moment it enters the body and starts actively fighting it, so the virus is much less likely to replicate and infect others. The lower the viral load, the lower the chance of forward transmission.

Once a sizeable portion of the population is vaccinated, the pandemic should gradually die out, as the virus runs out of new hosts – the effect may already be noticeable in Israel, which organized one of the fastest vaccination campaigns on the planet. In the mean time, let’s keep in mind that there is still quite a long road ahead of us before achieving vaccine-induced herd immunity. We should not let our guard down or celebrate prematurely until the virus is all but eradicated, especially considering the worrying reports of several mutations spreading faster than the original virus.

The case of rotavirus—which causes severe vomiting and watery diarrhea and is especially dangerous to infants and young children—is fairly straightforward. Vaccination limits, but does not stop, the pathogen from replicating. As such, it does not protect against mild disease. By reducing an infected person’s viral load, however, it decreases transmission, providing substantial indirect protection. According to the Centers for Disease Control, four to 10 years after the 2006 introduction of a rotavirus vaccine in the U.S., the number of positive tests for the disease fell by as much as 74 to 90 percent.

Stacey McKenna

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