COVID-19: Cases are dropping thanks to vaccines, real-world data shows
Just one dose of either the Pfizer/BioNTech or AstraZeneca vaccines cuts infection, experts say.
Vaccines should be able to control the COVID-19 pandemic, experts have said, as they published new real-world UK data showing jabs slash infection and are likely to cut transmission.
Just one dose of either the Pfizer/BioNTech or AstraZeneca vaccines leads to a two-thirds drop in coronavirus cases and is 74 per cent effective against symptomatic infection. After two doses of Pfizer, there was a 70 per cent reduction in all cases and a 90 per cent drop in symptomatic cases – these are the people who are most likely to transmit coronavirus to others.
Experts are still collecting data on two doses of AstraZeneca but say their findings show that both coronavirus vaccines work and are effective in the real world.
One of the new studies, which has yet to be peer-reviewed, is based on data from the national COVID-19 Infection Survey run by the University of Oxford and the Office for National Statistics (ONS). It included a random sample of more than 373,000 adults from across the UK, who produced more than 1.6 million swab test results between December and April.
Professor Sarah Walker, from the University of Oxford and chief investigator for the survey, said the study suggested vaccines could reduce transmission and were also effective against the Kent coronavirus variant.
“Showing that the benefits are greater both for people with high viral load and for people with symptoms, both of whom have probably got the greatest chance of onward transmission, was really not necessarily something I was expecting and… I was pleasantly surprised,” she said.
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The data showed a 57 per cent drop in infections among people not experiencing symptoms after one vaccine dose.
Dr Koen Pouwels, senior researcher at Oxford University’s Nuffield Department of Population Health, said the experts were “fairly confident” that the vaccines reduced onward transmission of the virus.
“However, the fact that we saw smaller reductions in asymptomatic infections than infections with symptoms highlights the potential for vaccinated individuals to get COVID-19 again, and for limited ongoing transmission from vaccinated individuals, even if this is at a lower rate,” he said.
“This emphasises the need for everyone to continue to follow guidelines to reduce transmission risk, for example through social distancing and masks.”
Walker said she was “cautiously optimistic” that the pandemic could be controlled long term with vaccines. She argued that “lockdown isn’t a viable solution” in the long term and vaccines are “clearly going to be the only way that we are going to have a chance to control this long-term.”
However, she said the “virus is very good at throwing us curveballs” and “we’re always going to be one small step away from the potential for things to go wrong again”.
In a separate study published by the team also as a pre-print, just one dose of AstraZeneca or Pfizer produced “strong antibody responses” in 95 per cent of people given a vaccine. While the Pfizer and AstraZeneca jabs behave differently in the early stages, both vaccines produced antibody levels that were sustained for at least 10 weeks.
Professor David Eyre, from the University of Oxford, said this supported the UK’s decision to delay second doses by up to 12 weeks.
Two doses of the Pfizer/BioNTech vaccine were also found to offer similar levels of protection against COVID-19 as for people who had had COVID previously.
Furthermore, the data showed that vaccination was just as effective in people over 75 or with underlying health conditions, as it was in those without or who were under 75. And while everyone showed at least some response to both vaccines, fewer than 5 per cent of people had low responses to both vaccines.
The researchers said there was a need to monitor this group’s response to a second vaccination.
"In older individuals, two vaccine doses are as effective as prior natural infection at generating antibodies to the virus that causes COVID-19 – in younger individuals a single dose achieves the same level of response," said Eyre.
“Our findings highlight the importance of individuals getting the second vaccine dose for increased protection.”
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