Oxford and Astra are the first vaccine developers to reveal data on asymptomatic infection rates.
Highlight
- Reducing the spread of the virus is a key element for the reopening of economies
- Oxford, Astra are the first to reveal data on the rate of asymptomatic infection
- Overall, it reduced such transmissions by 27% in a large study.
A vaccine from the University of Oxford and AstraZeneca Plc shows only a limited ability to stop coronavirus transmission despite preventing Covid-19 disease in the majority of those infected.
As promising vaccine data continues to come in, one of the central unanswered questions has been whether vaccines can not only prevent people from getting sick, but also slow the spread of the virus – a key element in reopening economies.
Oxford and Astra are the first vaccine developers to reveal data on asymptomatic infection rates in people who received the injection. Overall, it reduced such transmissions by 27% in a large study, according to peer-reviewed results published in the Lancet medical journal on Tuesday.
That’s well below the vaccine’s 70% effectiveness in preventing symptomatic cases of Covid-19 overall, although even those results are clouded by questions about its benefits in older recipients.
The researchers screened more than 6,000 study participants in the UK weekly for Covid-19 infections and found 29 asymptomatic infections in the vaccinated group. That compared to 40 cases in the control group, which was roughly the same size.
Smaller group
Vaccine efficacy against asymptomatic transmission was higher, 59%, in a smaller group that received half a dose, followed by a second full dose, rather than two full injections. The data support Oxford’s preliminary finding that the low-dose, full-dose regimen appears to elicit a stronger immune response, preventing 90% of infections. Two full doses were only 4% effective against asymptomatic transmission.
Although vaccines that prevent the disease but not transmission could be used widely and help reduce the number of deaths from the disease, they could also generate complacency in populations, experts say. Those who are immunized with them could still pass the virus to other more vulnerable people, including those who have not yet received a vaccine or cannot receive it for medical reasons.
Andrew Pollard, the Oxford professor who led the study, called the data “tempting” but said it was too early to draw firm conclusions. He said researchers are trying to test the amount of virus in the swabs to determine if vaccination reduces viral load, which would help limit spread.
“What would be great would be vaccines that prevent transmission to get to the point where not only people who are vaccinated are protected, but also those who cannot or have not yet been vaccinated,” he said. In an interview.
Similar questions surround other early Covid vaccines, including one from Pfizer Inc. and BioNTech SE that has been approved in the UK, where the first injections were given on Tuesday. The injection may not have worked as well in preventing asymptomatic cases as it did in preventing illness, according to a report by staff from the US Food and Drug Administration.
Pfizer expects to report data on whether or not its vaccine stops transmission of the virus in the first quarter of 2021, Chief Executive Officer Albert Bourla said.
(Except for the headline, this story has not been edited by NDTV staff and is posted from a syndicated feed.)
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