LONDON — The first study of the UK mass vaccination program showed strong evidence Monday that the coronavirus vaccine is working as expected. This is the most obvious sign to date that the vaccine can reduce the admission rate of Covid-19 hospitals. And may reduce the spread of the virus.
The British study found that a single dose of AstraZeneca vaccine or Pfizer vaccine can avoid most coronavirus-related hospitalizations, although the researchers said that it is not yet possible to accurately estimate this effect.
The results of research on AstraZeneca vaccines are the first to appear outside of clinical trials and represent the strongest signal of the effectiveness of vaccines used to stop the pandemic in most countries in the world so far.
This discovery strengthens and exceeds the scope of Israeli research. Israel also reported that the vaccine developed by Pfizer and BioNTech was not only used in clinical trials last year, but also provided effective protection against viruses in the actual environment. No other big country vaccinates people as quickly as the United Kingdom. It is the first country in the world to authorize and start using Pfizer injections and injections developed by AstraZeneca and Oxford University.
Studies released on Monday-two injections of Pfizer and two injections of AstraZeneca-showed that the two vaccines are effective against more infectious variants of the coronavirus that are circulating in the UK and spreading around the world.
Professor Aziz Sheikh of the University of Edinburgh said: “Both tools work very well.”
Despite this, the findings still contain some warning signs. Even when British legislators invoked the strength of vaccines to announce the gradual relaxation of blockade restrictions, government scientists also warned that more people need to be injected to prevent cases from spreading to vulnerable, vaccinated populations and occasionally causing serious illness and death. .
The UK has decided to postpone the second vaccination of Pfizer and AstraZeneca until up to three months after their first vaccination, in order to provide more people with partial protection from one injection.
Judging from the evidence released on Monday, the trade-offs involved in the strategy are not completely clear, but government scientists said that the sharp drop in hospitalization rates justified the strategy.
But the research results also show that people can be better protected from coronavirus infection after the second dose. They offered different answers to the question of how long a single dose of high protection level can last.
Professor Arne Akbar, University College London and Chairman of the British Society of Immunology, said: “We now need to understand how long a dose of vaccine can last for protection.”
A new study looked at approximately 19,000 health workers in England who received Pfizer vaccines. Scientists are able to monitor subjects very closely for infection: they are regularly tested for the virus, and asymptomatic cases can be found regardless of whether they show symptoms.
In contrast, many clinical trials only measure symptomatic infections.
The study showed that a single dose of Pfizer vaccine reduced the risk of infection by approximately 70%. Scientists said that after two doses of the vaccine, the protection rate increased to 85%, although they warned that it is difficult to estimate accurately due to the small number of cases.
Pfizer vaccines also seem to be very effective in the elderly. They are not highly representative in clinical trials and do not always respond strongly to the vaccine. Among people over 80 years old in England, a separate study showed that a single dose is effective in preventing symptomatic Covid-19 cases at 57%. After the second dose, the protective effect rose to 88%.
Elderly people who received the first dose of the vaccine but were still sick at least two weeks later had a much lower chance of being hospitalized or dying than unvaccinated patients, suggesting that the Pfizer vaccine weakened the impact of infection even if it did not completely prevent the infection. .
Dr Mary Ramsey, head of public health immunization in the UK, said that despite this, some vaccinated people were hospitalized or killed by the virus, which reminded people that “protection is not perfect yet.”
A study conducted in Scotland covered injections from Pfizer and AstraZeneca. The results of the AstraZeneca vaccine were even more limited, as the vaccine was later approved in the UK and was only put into use in early January.
Researchers there examined about 8,000 coronavirus-related hospitalizations and studied the difference between the risk of hospitalization for people with and without the vaccine.
The researchers said that the number of people who go to the hospital for vaccination is very small, and they can only make a very rough estimate of the effectiveness of the vaccine, but cannot compare the vaccines with each other.
But from 28 days to 34 days after the first injection, when it appeared to be at or near its peak efficacy, the AstraZeneca vaccine reduced the risk of hospitalization in a Covid-19 hospital by approximately 94%. During the same period, Pfizer vaccine reduced the risk of hospitalization by approximately 85%, although in both cases the number was too small to determine the exact effect.
These findings are reassuring signs of the effectiveness of AstraZeneca’s vaccine, which is the backbone of many national vaccination programs. Its production cost is much cheaper and it is different from Pfizer vaccine. The Pfizer vaccine is a vaccine produced by Hyundai. The vaccine has not been used in the UK. It can be transported and stored in a normal refrigerator.
But the British study cannot solve the high level of protection that a single dose of Pfizer or AstraZeneca vaccine can achieve.
In the Scottish study, people’s risk of being hospitalized within a week after receiving the first shot decreased, and reached its lowest point four to five weeks after vaccination. But then it seemed to rise again.
Simon Clarke, professor of cellular microbiology at the University of Reading, said: “The peak period of protection is four weeks, and then it starts to decline.”
In England, there is no evidence that the level of protection has declined after one month. Scientists say that more evidence is needed to determine whether the protection provided by a single dose is likely to disappear, and how quickly it disappears.
In parts of Europe, the AstraZeneca vaccine has been suspected. Due to the lack of clinical trial data in this group, many countries choose not to give it to the elderly.
The Scottish study cannot provide accurate figures on the effectiveness of the vaccine for the elderly. But the vaccination program there has greatly reduced the number of hospitalizations for people over the age of 80, and many elderly people have been vaccinated with AstraZeneca.