- The effectiveness of the Covid-19 vaccine declined in less than six months.
- The Zoe Covid study found that the AstraZeneca vaccine dropped from 77% one month after the second vaccination to 67% four to five months later.
- Pfizer’s vaccine is 88% effective one month after the second vaccination, but 74% after five to six months.
According to a study on data from mobile apps on Wednesday, the protective effects of the Pfizer and AstraZeneca vaccines against the two doses of vaccine diminish in less than six months, suggesting that intensified injections may be needed to ensure extended coverage.
The latest discovery comes when several countries have introduced additional vaccines for fully vaccinated people. The World Health Organization has criticized this initiative because millions of people in the world have not yet received a dose of the vaccine.
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According to the latest analysis of Zoe Covid research data, Pfizer’s effective rate is 88% one month after the second dose, but the protection rate drops to 74% after five to six months.
The study used real-world data collected through a mobile phone app, which has more than one million active users who recorded details of their vaccinations and test results, which were then conducted by scientists including scientists at King’s College London Researchers conduct analysis.
The research draws on more than 1.2 million test results and participants.
‘Reasonable worst case’
The protection rate of the AstraZeneca vaccine dropped from 77% one month after the second dose to 67% four to five months later.
Professor Tim Spector, the chief scientist of the Zoe app, said that more data is needed on how vaccine effectiveness varies among different age groups.
After the social restrictions were lifted in July, the number of cases in the UK increased sharply, but the number of hospitalizations remained stable last month.
But Spector, a professor of genetic epidemiology at King’s College London, warned that the decline in vaccine effectiveness among the most vulnerable populations could lead to an increase in hospitalizations and deaths in the winter.
“In my opinion, in a reasonable worst-case scenario, in winter, the protection of the elderly and medical staff may be less than 50%,” he said.
The scientist said that if the infection rate remains high despite the more contagious Delta variant and the relaxation of restrictions, “this situation may mean an increase in hospitalizations and deaths.”
“We urgently need to develop a vaccine boost plan,” Specter added.
He also said that if our goal is to reduce the number of deaths and hospitalizations, the UK needs to decide whether its current focus on child vaccination is “wise.”
The latest findings came after another study published by Oxford University scientists last week found that the effectiveness of Pfizer vaccines declined faster than that of AstraZeneca.
The United Kingdom began to vaccinate the elderly or clinically susceptible people in December 2020, so these people account for the majority of the population that has been fully vaccinated for half a year, and the risk of infection may now increase.
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