Pfizer and Moderna's Covid-19 vaccines are less effective at preventing senior citizens with the delta coronaviruses variant from getting sick than the shots themselves, according to a new study.
A study found that protection against infections fades after four months for Pfizer and Moderna shots.
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After the final shot, the effectiveness of the vaccine fell to less than half of what it was before, according to an analysis of health records from over 14,000 Covid-positive male veterans over the age of 65.
The protection against infections fell to less than half in the first month after the second shot and to less than half by the third month.
vaccine effectiveness fell to a low of 20% in months five through seven after the third month, when the researchers were only able to do it during times of high delta transmission.
The researchers said that the decrease could be due to increased transmission of the delta variant and waning vaccine immunity.
The researchers said that the study's focus on older male veterans should be considered if trying to generalize the findings.
Booster shots, an additional dose of vaccine following the initial course, are frequently deployed in medicine as a way of counteracting the effects of vaccine immunity waning over time. One day, it is possible that the definition of fully vaccineed will be expanded to include a third coronaviruses vaccine shot. It's important to prevent the spread of disease, but it's not the only purpose of vaccination. The vaccines are still effective at preventing serious illness, hospitalization and death from Covid-19, and experts believe there is strong evidence that the vaccines still do this.
The shots still offer strong protection against severe disease, despite the fact that they are less effective at preventing infections with the omicron variant. More information will emerge over time as research into omicron progresses.
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