According to a new study, the protection conferred by two doses of the Pfizer and AstraZeneca vaccines can begin to wane after six months. In the worst-case scenario, protection for the elderly and healthcare professionals would drop to less than 50% by winter since they were the first to receive the vaccination. According to the research, the Pfizer vaccine was shown to be 88 percent effective at preventing illness a month after the second dosage. However, after five to six months, the efficacy dropped to 74%. This would imply that protection would drop by 14% after four months.
The Astra Zeneca vaccination was also examined in the ‘Zoe’ Covid-19 trial. It originally provided 77 percent protection one month following a second dosage. After four to five months, it, too, dropped to 67 percent. A ten-percentage-point drop. Experts suggest that reduced vaccination protection over time is to be expected. More than 1.2 million test data and volunteers were used in the study.
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More than four months following the second dosage, there was an 83.7 percent reduction, a 12.5 percentage point risk reduction. Real-world testing is likely to demonstrate lower protection than clinical trials, and the vaccinations were not tested against the virus’s now-dominant Delta form. While protection tends to diminish over time, researchers note that individual risk may vary due to differences in antibody duration.
When the Pfizer vaccine was authorized at the end of last year, the most vulnerable people and front-line health care professionals were given priority. This might indicate that most patients who received their second dosage five to six months ago are older or susceptible. This might indicate that these persons are now at a higher risk of contracting Covid-19 than those vaccinated more recently. More data over a longer period is needed, according to researchers, to clearly say how vaccination efficacy varies over time and across age groups.
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Vaccines, however, give significant levels of protection, particularly against the Delta form, and can lower the risk of severe disease. “A plausible worst-case scenario, in my opinion, could see protection for the elderly and healthcare professionals below 50% by winter,” said Professor Tim Spector, principal scientist on the Zoe Covid Study app.
