Omicron may raise reinfection risk; booster protection documented
Omicron may raise re-infection risk; booster protection documented
December 6, 2021; 3:54 PM EST
A booster shot of the Pfizer/BioNTech COVID-19 vaccine appears to provide strong protection, at least in the short term, according to data from Israel. The odds of testing positive for the coronavirus were much lower in adults who received a third dose of the vaccine than in people who got their second dose more than five months ago, the data showed. Researchers with Maccabi Health Services reviewed data on PCR tests performed in more than 306,000 adults after the Pfizer/BioNTech booster dose became widely available. Roughly half the tests were done in people who had received a booster and half in people who had received only the standard two doses, with at least five months since the second dose. Overall, 1.8% of tests were positive in the booster group, versus 6.6% among those with only two doses, the researchers reported last week in the journal JAMA Internal Medicine. After taking participants’ various risk factors into account, they estimated that between four and nine weeks after receipt, the third shot was associated with an 86% reduction in the odds of testing positive for the virus. Results were similar when the researchers compared subsets of closely matched recipients of two or three doses. The vaccine’s waning of protection over time “seems to be counteracted in the short-term by a third dose,” but longer monitoring is needed to see how long the protection will last, the researchers said.
Rare cardiac effect of vaccine usually improves quickly
The few pediatric recipients of COVID-19 vaccines who develop a heart muscle inflammation known as myocarditis are likely to have mild symptoms that improve quickly, according to a report published on Monday in the American Heart Association (AHA) journal Circulation. The rare side effect has been most often reported among adolescent and young adult males. Researchers reviewed data from 26 children’s hospitals across the United States and Canada, focusing on 49 patients ages 12 to 20 who were hospitalized for “confirmed” myocarditis within a month of receiving the vaccine, and 91 with “probable” myocarditis. Most (91%) were male, 66% were white, and the average age was about 16. While 19% required intensive care, no one died. Half of the patients were sent home within two days. While COVID-19-vaccine-related myocarditis is usually mild and usually resolves quickly, the condition is nevertheless “a cause of great concern,” and it is not clear yet how patients do over the long term, the researchers said. Still, they concluded, “its risk must be balanced against critical illness and cardiovascular involvement” associated with COVID-19. In a press statement, AHA President Dr. Donald Lloyd-Jones, who was not involved in the study, said that data has shown that the benefits of COVID-19 vaccination “far exceed the very rare risks of adverse events, including myocarditis.”
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