Pfizer’s Covid vaccine still works against the South African and Brazilian variants of the virus, studies today suggest.
The shot prevented 100 percent of infections in a study conducted by Pfizer in South Africa, and British lab tests on the Brazilian P1 strain of the virus found it to work against it.
Scientists were concerned that new variants of the virus would make vaccines less effective because they change shape and make it harder for the body to recognize.
Recent laboratory studies have shown that levels of beneficial virus-fighting antibodies drop when vaccinated people are exposed to new variants, but scientists now say that this does not appear to affect actual immunity.
One researcher said their study of the elderly saw antibody levels were ‘off the scale’ after two doses and everyone was developing signs of protection.
And Pfizer reported that the results of its clinical trials showed “high vaccine effectiveness against the variant found in South Africa.”
The findings are good news for long-term confidence in the shot and suggest that boosters may not be as important as the first two doses. It also raises the prospect that international travel won’t be too dangerous because the threat of variants is less.
Pfizer’s vaccine has been given to about 11 million people in the UK and is an important part of the rollout, balanced by AstraZeneca shots (pictured: man receives vaccine in Derby)
A University of Birmingham study looked at how well the shot – the first to be approved and now given to about 11 million Britons – worked in people over 80.
It was found that all 100 80-96 year olds in the study developed antibodies after vaccination and 98 of them had “strong” responses.
The scientists behind the study said the number of antibodies – virus-destroying proteins made by the immune system – in their study were “abnormal” and they were “delighted” with how well the vaccine seemed to work.
Vaccines have not been widely tried in the elderly because early studies usually focus on low-risk patients and the immune system of the elderly is generally worse.
In addition to additional evidence that the shot protects elderly people most at risk from Covid, the study also found that it should work against the Brazilian P1 variant of the virus.
Immune responses to P1 were weaker but still high enough to prevent serious illness, the study found.
The South African variant, which is more widespread in England with 412 cases compared to 27, was not looked at, but admitted that it was ‘potentially more concerning’. The variants are very similar.
The study measured their immune response with blood samples taken just before the second dose and then two weeks after.
The study began before the UK changed its policy to a 12-week interval between doses, so anyone enrolled got a second shot after three weeks, but Dr. Helen Parry said, “I would expect similar end results once those vaccines are given.”
All of the people in the study had antibodies in their blood two weeks after the second dose of Covid, and two-thirds had them after a single dose.
The presence of antibodies in the blood suggests that the body is ready to fight the virus and that someone is immune to Covid, at least to disease if not completely.
And Dr. Parry and her colleague Professor Paul Moss, both from the University of Birmingham, said they were surprised by the number of antibodies people had.
“When we sent these samples to Porton Down, they said we can’t give you the results now because we have to dilute them because they’re so high,” said Professor Moss.
‘They’re off the scale.
The antibody levels were so high that they passed the threshold [of blood tests] so we had to dilute them. ‘
Dr. Parry added: “It was very exciting. And even the response to the first vaccine, we were very happy with that. ‘
The University of Birmingham study found that people still had antibodies that could destroy the Brazilian variant (green) – they were lower than against the Wuhan strain, but still enough to stop the disease, the researchers said.
For people who had already contracted coronavirus before receiving the Pfizer vaccine, antibody levels spiked with the first dose (blue lines). For people who had never had the virus, protection started after the first dose and was enhanced by the second (red lines)
About one in 10 people in the Birmingham study had already had Covid before the vaccine (blue) and these were the people who developed the most antibodies, illustrated by the bar graph
It was not clear how well vaccines would work in very older people, because the immune system gets weaker with age and does not respond as well to injections.
While everyone had strong antibody responses, only 63 percent of people had measurable levels of T cell white blood cells after their shot.
These are cells that can destroy virus-infected cells and control antibody production in the long term, and are believed to be important for long-term protection.
Dr. Parry said researchers had seen an “excellent cellular response” in younger people, “probably suggesting this is an effect of aging.”
But more positive news, the study suggested the vaccine would protect people from the Brazilian P1 variant.
P1 has been developed in a way that appears to make the immunity designed for the Wuhan variant of the virus less effective, in the same way as the South African strain.
This study found that effective antibody levels were 14 times lower against P1, but still high enough to protect against Covid disease.
Dr. Parry said, “Our study provides further evidence that the mRNA vaccine platform provides a strong immune antibody response in humans up to 96 years old and maintains broad efficacy against the P1 variant, which is a variant of concern.”