3 studies guiding the US booster plan

HHS said the country's booster plan, announced Aug. 18, was based on data that made it "very clear" COVID-19 vaccines' protection wanes over time. 

The department said it is prepared to offer booster shots for all Americans who received two doses of Pfizer or Moderna's COVID-19 vaccine beginning the week of Sept. 20 and starting eight months after an individual's second dose.

To form this plan, federal scientists gathered the data over the past several months. The CDC released three key studies Aug. 18 demonstrating that while COVID-19 vaccines' protection against infection declines over time, they still offer strong protection against hospitalization and death. 

The real-world studies gathered their data from three different sources. Below is a breakdown of what they found:

Nursing homes and long-term care facilities

One study examined reported infections among Americans who lived in nearly 15,000 nursing homes and long-term care facilities and received two doses of Pfizer's or Moderna's COVID-19 vaccine. It found the vaccine's protection against COVID-19 decreased to 74 percent during March, April and early May, and dropped to 53 percent in June and July.

The study considered all COVID-19 infections, regardless of whether they were symptomatic. The researchers said it was unclear how much the declining efficacy rates can be attributed to the delta variant.


Another study examined data from 21 hospitals in 18 states on 1,129 patients who were fully vaccinated with Pfizer's or Moderna's vaccine. 

It found the vaccines demonstrated 86 percent efficacy in protecting against COVID-19-related hospitalization at two to 12 weeks after the second dose was administered. The figure dropped by just two percentage points at 13 to 24 weeks after the second shot.

New York

This study analyzed protection against hospitalization and infection among people who lived in New York and were fully vaccinated with Pfizer's or Moderna's vaccine. From May 3 - July 25, protection against hospitalization hovered around 92 percent to 95 percent. During the same time period, protection against infection declined from 92 percent to 80 percent.

The researchers noted the decline in protection against COVID-19 infection came at the same time as social distancing and masking policies were relaxed, as well as the spread of the delta variant.


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