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A single dose of Pfizer’s coronavirus vaccine is “highly protective” after three weeks, according to a study.
Researchers at the University of East Anglia (UEA) said the coronavirus vaccine developed by Pfizer and BioNTech was still effective after 21 days without a dose of “ supplement ” within the recommended time frame.
It comes after a study found that the Oxford coronavirus vaccine offers 76% protection for up to 12 weeks after a single dose and can reduce transmission by 67%.
The UEA study on the Pfizer vaccine, which has not yet been peer-reviewed, looked at data from Israel where the vaccine was deployed. Scientists have found that the vaccine becomes 90% effective after 21 days – supporting UK plans to delay the timing of a second vaccine.
While it is not yet known how long the immunity lasted beyond 21 days without a second dose, researchers believe it is “unlikely” to decline significantly over the next nine weeks. .
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But scientists warned that people’s risk of infection doubled in the first eight days after Pfizer’s vaccine, citing people becoming less cautious as a possible cause.
“A recent unpaired pre-print article based on Israel’s experience examined data from 500,000 people who had received the Pfizer vaccine. He pointed out that a single dose may not provide adequate protection, ”said lead researcher Professor Paul Hunter of the Norwich Medical School, UEA.
“But we saw a number of shortcomings in the way they looked at the data, including the fact that they did not attempt to estimate the effectiveness of the vaccine from day 18. That would have given a better indication of the effectiveness of a single dose of the vaccine if the second dose was delayed up to 12 weeks. “
The researchers analyzed the data to see the impact of Israel’s vaccination program on the number of cases, and then estimated the vaccine’s effectiveness over time. They found that after the initial vaccination, the number of cases increased for eight days before dropping “to low levels” by day 21.
“Surprisingly, the daily incidence of cases increased sharply after vaccination until about day 8 – roughly doubling,” Professor Hunter said.
“We don’t know why there was this initial surge in infection risk, but it may be because people are less careful about maintaining protective behaviors as soon as they get the injection. We found that the efficacy of the vaccine was still virtually zero until about 14 days after vaccination of people, ”he said.
“But then, after day 14, immunity gradually increased day by day to about 90 percent by day 21 and then didn’t improve any more. Any improvement observed was before any second injection. This shows that a single dose of vaccine is highly protective, although it can take up to 21 days to achieve this.
“And he supports the UK policy of widening the dose gap by showing that a single dose can provide a high level of protection.”
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He added: “While we don’t know how long this immunity will last beyond 21 days without a second booster, we are unlikely to see a major drop in the next nine weeks.”
The government has been criticized for its decision to delay the timing of the second dose of COVID-19 vaccines for up to 12 weeks after the first, with some raising concerns about the level of immunity from a single injection.
The University of Oxford announced on Tuesday February 2 that its study, which has not yet been peer reviewed, found that the vaccine’s efficacy from two doses was 82, 4% with an interval of three months.
His results also indicate that those who have been vaccinated are not only protected against the disease, but are also not likely to pass the virus on to anyone.
How do scientists develop vaccines against new viruses?
Vaccines work by tricking our bodies into believing that we have been infected with a virus. Our body sets up an immune response and builds a memory of this virus that will allow us to fight it in the future.
Viruses and the immune system interact in complex ways, so there are many different approaches to developing an effective vaccine. The two most common types are inactivated vaccines (which use harmless viruses that have been “ killed ” but still activate the immune system), and attenuated vaccines (which use live viruses that have been modified to trigger an immune response without causing us harm).
A more recent development is that of recombinant vaccines, which involve the genetic engineering of a less harmful virus so that it includes a small part of the target virus. Our body launches an immune response to the carrier virus, but also to the target virus.
In recent years, this approach has been used to develop a vaccine (called rVSV-ZEBOV) against Ebola virus. It is an animal vesicular stomatitis virus (which causes flu-like symptoms in humans), designed to contain an external protein from the Zairian strain of Ebola.
Vaccines go through a considerable amount of testing to make sure they are safe and effective, if there are any side effects, and what doses are suitable. It usually takes years for a vaccine to be available on the market.
Sometimes it takes too long, and the new Ebola vaccine is given on “compassionate use” terms: it has not yet completed all of its formal testing and paperwork, but it has proven to be safe and effective. Something similar might be possible if one of the many groups around the world working on a vaccine against the new strain of coronavirus (SARS-CoV-2) is successful.
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