To the contrary, doctors and public health experts expect things like this to happen to some people.
Emergency nurse Matthew W. (who has only been identified with his last initial) told local station ABC 10News that he tested positive on Dec. 26 after starting to feel sick on Christmas Eve with muscle aches, chills and fatigue.
The 45-year-old had received his first shot of the Pfizer vaccine on Dec. 18. But his illness should not sound any alarm bells.
Both of the vaccines approved for use in the United States so far ― manufactured by Pfizer and Moderna ― require a patient to get two shots, spaced a certain number of days apart. People receiving the Pfizer vaccine are told to wait 21 days before getting their second jab.
The drugs have been praised for their high efficacy rate ― around 95% each ― but that’s only if you get both shots. After one shot, available data suggests the Pfizer vaccine has about 50% efficacy. Medical professionals use the term “efficacy” to describe the proportionate reduction in cases of COVID-19 among vaccinated people. The word is basically synonymous with “effectiveness” (although researchers will sometimes impose slightly different definitions).
It is therefore likely that some people will contract COVID-19 between their first and second shots. In that period, like Matthew W., they will have only about a 50% reduced risk of becoming sick.
It’s also likely that some people will contract COVID-19 after the second shot ― the vaccines do not offer 100% protection.
Additionally, it is possible that Matthew W. had caught the virus before receiving his first shot, because it can take up to two weeks for people to start feeling symptoms.
All of this is a big part of the reason why public health experts are discouraging people from immediately resuming their normal lives after they get vaccinated.
Researchers are confident, however, that the vaccines will offer a high degree of protection to a lot of people as more and more of the population is inoculated. As that happens, scientists expect to gain an even clearer understanding of the protection that each vaccine offers.
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