The first studies of Britain’s comprehensive vaccination program showed, on Monday, strong evidence that coronavirus vaccines were working as intended, and provided among the clearest signs to date that vaccines are reducing the rate of hospitalization of Covid-19 and possibly reducing virus transmission. .
One dose of either AstraZeneca Vaccine British studies have found that or those made by Pfizer can avoid most hospitalizations related to the Coronavirus, although the researchers said it was too early to give accurate estimates of the effect.
AstraZeneca’s findings, the first to appear outside of clinical trials, represent the strongest indication yet of the efficacy of the vaccine that much of the world relies on to end the pandemic.
And separate studies of the Pfizer vaccine have provided confusing new evidence that a single dose may reduce the spread of the virus, showing that it not only prevents symptomatic cases of Covid-19 but also asymptomatic infections.
The results reinforced and surpassed studies from Israel, which also reported that a vaccine developed by Pfizer and BioNTech provided significant protection from the virus in real-world conditions, not just in clinical trials conducted last year. There is no other great nation People get vaccinated as quickly as in Britain, And was the first country in the world to authorize and begin using both the Pfizer snapshot and those developed by AstraZeneca and the University of Oxford.
Studies released on Monday – two on a Pfizer syringe, one on one and one on AstraZeneca – showed that the two vaccines were effective against the most contagious coronavirus variant that had spread in Britain and spread worldwide.
“They both work very well,” said Aziz Sheikh, a professor at the University of Edinburgh who helped conduct the Scottish vaccine study.
However, the results contained some warning signs. Even as British lawmakers cited the power of vaccines in the advertisement Gradual easing of lockdown restrictionsGovernment scientists have warned that more people need injections to prevent cases from spreading to vulnerable and immune groups and sometimes causing serious illness and death.
Britain has decided to delay giving people second doses of the Pfizer and AstraZeneca vaccine for up to three months after the first doses, and has chosen to provide partial protection to more people from a single dose.
The trade-offs involved in this strategy were not entirely clear from the evidence released on Monday, but government scientists said the sharp decline in hospitalization rates justified the strategy.
But the results also indicate that people are more protected from the Corona virus after a second dose. They provided mixed answers to the question of how long levels of protection persist from a single dose.
“We now need to understand how long this protection lasts for one dose of vaccine,” said Arne Akbar, professor at University College London and president of the British Society of Immunology.
One new study looked at about 19,000 health workers in England who had received the Pfizer vaccine. Scientists were able to observe uncommonly closely about whether or not people had been infected: they were regularly tested for the virus, whether or not they showed symptoms, allowing scientists to spot asymptomatic cases.
By contrast, many clinical trials have measured only asymptomatic infections.
That study showed that a single dose of the Pfizer vaccine reduced the risk of infection by approximately 70 percent. Scientists said that after two doses of the vaccine, protection had risen to 85 percent, though they cautioned that the small number of cases made it difficult to come to accurate estimates.
The Pfizer vaccine has also been shown to be effective in older adults, who are not well represented in clinical trials and do not always have strong responses to vaccines. In people over 80 in England, a separate study showed that a single dose was 57 percent effective in preventing symptomatic cases of Covid-19. Protection increased to 88 percent after a second dose.
Older adults who received a first dose of the vaccine and were still getting sick after at least two weeks had significantly lower odds of being hospitalized or dying than the unvaccinated, indicating that the Pfizer vaccine reduced the effect of infection even when it did not stop it completely.
However, some people who had been vaccinated were hospitalized or died from the virus, in a reminder that “protection is not complete,” said Dr Mary Ramsay, head of immunization at Public Health England.
A study in Scotland included the injections Pfizer and AstraZeneca. Results on the AstraZeneca vaccine were limited because it was subsequently licensed in Britain, and it only came into use in early January.
Researchers examined about 8,000 hospitalizations due to the Corona virus, and studied how the risk of hospitalization differs between people who did not receive an injection.
The researchers said the numbers of people who had been vaccinated and who sought care in hospitals were so small that they could only produce very rough estimates of the effectiveness of the vaccines, and were unable to compare the shots with each other.
But 28 to 34 days after the first shot, when it appeared to have reached or near peak effectiveness, the AstraZeneca vaccine reduced the risk of hospitalization for Covid-19 by about 94 percent. In the same time period, the Pfizer vaccine reduced the risk of hospitalization by nearly 85%, although the numbers in both cases were too small to be confident of the exact effect.
The results were a reassuring sign about the effectiveness of the AstraZeneca vaccine, which is the backbone of vaccination plans in many countries. It is much cheaper to produce, and unlike the Pfizer vaccine – and one from Moderna, which has not yet been used in Britain – it can be shipped and stored in regular refrigerators.
But British studies could not say how long high levels of protection would last from a single dose of the Pfizer or AstraZeneca vaccine.
In the Scottish study, the reduction in the risk of people being hospitalized began a week after they had received their first vaccine, and reached a low point four to five weeks after they were vaccinated. But then it seemed to rise again.
“The maximum protection level is four weeks, then it starts to regress,” said Simon Clark, a professor of cellular microbiology at the University of Reading, who was not involved in the study.
In England, there was no evidence of reduced levels of protection after a month. Scientists said more evidence is needed to determine whether the protection afforded by a single dose is likely to diminish, and how quickly.
AstraZeneca vaccine has encountered suspicions in parts of Europe; Many countries chose not to administer it to the elderly, citing a lack of clinical trial data in that group.
The Scottish study was unable to provide accurate figures on the effectiveness of the vaccine in the elderly. But the vaccination program there has dramatically reduced hospitalization for people over the age of 80, and many elderly people have been given the AstraZeneca vaccine.