Single dose of Pfizer vaccine blocks three-quarters of asymptomatic infections, study finds

Single dose of Pfizer / BioNTech coronavirus vaccine can block 75% of asymptomatic infections, suggested a study of UK National Health Service (NHS) workers.

An asymptomatic assessment by staff at Addenbrooke’s Hospital in Cambridge showed that the number of people who tested positive decreased from 0.8% to 0.2% 12 days after the first injection.

The results described as “very impressive” by local authorities are another sign that Britain’s attempt to delay the second dose in the aim of wider and faster vaccination coverage has paid off.

As they explained, reducing asymptomatic infections is essential to prevent new infections from developing unknowingly, as people who do not feel sick are less likely to isolate themselves.

Many studies had indicated that a single injection of the vaccine from the American company Pfizer and the German company BioNTech prevented serious illness and death, but it was not clear to what extent it blocked asymptomatic spread. Research has also suggested that the University of Oxford / AstraZeneca inoculant stops more than 60% of asymptomatic cases.

The study, led by the University of Cambridge, analyzed thousands of weekly COVID diagnostic tests at Cambridge University Hospitals NHS Foundation Trust in January.

In this analysis, the scientists found that 26 of 3,252 swabs (0.8%) from unvaccinated workers tested positive for their swabscompared to four of 1,989 (0.2 percent) of staff tested 12 or more days after their vaccination.

The study, which has not yet been peer-reviewed, also found that asymptomatic infection was halved in people vaccinated for less than 12 days, suggesting that immunity onset in many case.

Independent experts responding to prepress praised the results, saying they indicated the UK was heading for a “much brighter future“.

For the teacher Jonathan ball, molecular virologist at the University of Nottingham, “To see such a reduction in infection rates after a single dose of Pfizer vaccine is very impressive and shows that vaccination really offers a way out of the current restrictions and a much better future.“.

“It will be important to understand whether the reduction in the risk of infection was manifested in all of the exposure risk groups included in the study, but this is excellent news nonetheless,” he said. he adds. Daily mail.

According to what the doctor explained Simon clarke, associate professor of cellular microbiology at the University of Reading, “In adults of working age, Pfizer-BioNTech vaccine has good efficacy in preventing asymptomatic COVID-19 infection. This is really important if we are to reduce the amount of spread by people who do not know they are infected ”.

Although this is very encouraging, no data were provided to show the duration of the effect and continued monitoring is necessary if this protection is diminished“, a point.

Agregó que el estudio “surgió luego de estudiar al personal del NHS y parece que no se ha realizado una evaluación de su estado inmunológico preexistente, que podría haber sido más alto que en la población general dada la probabilidad de exposición de los trabajadores de la salud at work”. Pre-exposure to the coronavirus before receiving a dose appears to elicit a stronger immune response to the vaccine.

However, Clarke cautioned that “it is also important to remember that these results cannot be automatically extended to all other vaccines.”. Over a two-week period between Jan. 18 and Jan. 31, Cambridge researchers looked at similar numbers of vaccinated and unvaccinated staff using about 4,400 PCR tests per week. A positive PCR sample would indicate that even a vaccinated person has fragments of the virus in their nose or throat that could transmit the disease.

Reducing the spread is key to achieving “herd immunity” when so many people are immune that a disease goes away. The results were then separated to identify unvaccinated staff and staff who had been vaccinated more than 12 days prior to testing, when immunity kicks in.

It’s because of it When the team included symptomatic healthcare workers, their analyzes showed similar reductions. About 56 of 3,282 (1.7 percent) of unvaccinated healthcare workers tested positive, compared to eight in 1997 (04 percent) 12 days or more after vaccination, a four-fold reduction.

The researchers released their data ahead of the peer review due to the urgent need to share information related to the pandemic.

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