A new paper released this week, suggested that a vaccine developed by AstraZeneca and Oxford University can not only protect participants in clinical trials against the development of diseases, but can also significantly reduce the transmission of the virus that causes the disease.
In the recent outburst of data on Covid-19 vaccines, the proposal stood out. The question of whether Covid-19 vaccines reduce transmission is critical and unanswered, creating uncertainty as to whether vaccinated people can still be infected by SARS-Cov-2, the virus that causes Covid, to those who have not yet been vaccinated.
Media reports have seized a Oxford reference from researchers that a single dose of the vaccine cut the positive test results by 67%, pointing out that this is the first evidence that a vaccine can prevent the transmission of the virus . But the paper, which has not yet been judged by peers, proves it or does not claim it, although it does suggest the possibility.
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Instead, it has been shown that fewer people carry the virus as a result of being vaccinated. Fewer people carrying viruses, according to the researchers, equates to a reduction in the amount of viruses spreading in a community.
‘This data indicates [the AstraZeneca vaccine]’, used in the authorized schedules, could have a significant impact on the transmission by reducing the number of infected individuals in the population,’ the authors wrote.
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If someone tests negative, Andrew Pollard, one of the study authors and a professor of pediatric infection and immunity at the University of Oxford, told STAT in an email: ‘It’s a reasonable assumption that they can not transmit not.’
But it is a big and unjustified leap, experts from outside agree, from the proposal to a proof of reduced transmission of people being vaccinated.
‘The study shows a decrease in [viral] shedding, not ‘transmission’, ”said Carlos del Rio, a professor of infectious diseases at Emory University School of Medicine. “The end result is, no, no one can draw a conclusion or a straight line.”
Kathleen Neuzil, director of the Center for Vaccine Development at the University of Maryland School of Medicine, agrees.
“I think there are too many moving variables to make too much of a single result here,” she said. “However, the trend is consistent and in the right direction.”
The researchers who studied the Oxford-AstraZeneca vaccine did not want to see if people who received the vaccine were less likely to transmit the SARS-2 virus. However, they asked that each volunteer in one of their studies, which was done in the UK, weekly turn a swab into their nostrils from their nose to test for polymerase using polymerase chain reaction or PCR. None of the other major vaccine studies took the step as part of their protocols.
What they found was that while a single dose of the two-dose vaccine cut positive test results by 67% – the figure used in many media reports – two doses reduced the positive tests by 49.5%.
The deterioration is difficult to explain, and the Oxford article does not attempt to do so.
‘How can we explain it biologically? Does this show that the numbers cannot be compared directly? Asks Natalie Dean, a biostatistician who focuses on vaccines at the University of Florida, who noted that booster doses usually improve the performance of a vaccine and do not erode. ‘You only have certain expectations and it’s hard to understand. How will the efficiency decrease after an amplifier is received? ‘
More research is needed on the AstraZeneca vaccine, del Rio said, adding that current studies, first report on does not answer very important questions in December. Different perspectives on the study – a compilation of four different studies – have divided the world as the UK, much of Europe and India have approved the vaccine, while the US and Switzerland are awaiting more information.
A major U.S. study is being conducted with the U.S. government, similar to those conducted by Moderna and Johnson & Johnson. Results can only come at the end of February.
“I just keep telling my volunteers that the US study is the definitive study to tell us how this vaccine works against severe, hospitalized Covid and symptomatic Covid,” said Anna Durbin, a vaccine researcher at Johns Hopkins. . Bloomberg School of Public Health involved in the US trial of the AstraZeneca vaccine.
Unfortunately, in a pandemic, there is nothing more difficult than waiting.