According to the researchers, a single dose of the Oxford / AstraZeneca or Pfizer / BioNTech vaccine generates a large protective antibody response against coronavirus in people 80 years of age and older.
The first study to look at the comparative performance of the two vaccines that have been used in the UK in recent months shows that 93% of people develop antibodies to the coronavirus spike protein between five and six weeks after a single one. Pfizer injection, and% after a single AstraZeneca.
But researchers from the UK Coronavirus Immunology Consortium, which includes scientists from 20 different centers, found a difference in the cellular response elicited by vaccines. That is the generation of T cells that help fight the virus.
The AstraZeneca vaccine had a greater effect: 31% of people developed T cells against the spike protein compared to 12% of those who received the Pfizer injection. People who received the AstraZeneca injection also had a stronger cellular response.
The findings suggest that the UK policy of waiting 12 weeks between doses is safe, as the most vulnerable age group develops a strong antibody response to vaccines long before the second delayed dose. They say more work is needed to find out if the difference in cellular response is significant.
“It is important to understand how the immune response generated by Covid-19 vaccines varies with age, the delay between doses and the type of vaccine administered,” said Paul Moss, professor of hematology at the University of Birmingham and principal investigator of the consortium. . .
“To our knowledge, this study is the first of its kind to compare antibody and T-cell responses after a single dose of the Pfizer or AstraZeneca vaccine in any age group. The findings are reassuring because many countries, including the UK, have chosen to delay the administration of second doses. “
The study, published online as preprint by The Lancet, it has not yet been peer reviewed. The researchers analyzed blood samples from 76 people, ages 80 to 99, who received a single dose of Pfizer injection, and 89 who received the AstraZeneca vaccine.
Dr Helen Parry, a clinical academic professor at the University of Birmingham and first author of the paper, said it is important to study what happens to the immune system of older people after vaccination.
“The response to the Covid vaccine in the elderly is of particular interest to us because we know that the function of the immune system deteriorates with age. Vaccines are not always responded to as effectively as the younger population, but older people are also at the highest risk of severe Covid, ”he said.
“The UK and some other countries have chosen to delay the second dose to speed up population coverage. So in this high-risk group for Covid-19, we think it’s really important that we study immune responses to different vaccine platforms, but also different programs that are in the future. “
Eight people who had already had Covid-19 had a very strong immune response after a dose of vaccine: a nearly 700-fold increase in antibodies and a four-fold increase in T cells. “Previous natural infection actually improves immune responses to the vaccine. But all patients must receive both vaccines, ”Parry said.
Antibody responses are important against infection and reinfection, Moss said, “but the cellular response is more subtle.” T cells may protect against the severity of the disease, but they may also be less susceptible than antibodies to loss of variant immunity.
“I think people are confident that the variants will only lose 10-20% of the cellular response, whereas they can lose much more of the antibody response. It’s about how the immune system works, ”he said.
One possibility for the future is that vaccines can be “mixed and matched” so that people can have a pin prick that elicits a stronger cellular response and another that elicits a higher antibody count. A trial looking at combining these two vaccines in this way has just been expanded to include Moderna and Novavax jabs as well.
Meanwhile, a new study by the NHS and the University of Manchester found that older people who had received the Pfizer jab were less likely to be admitted to the hospital. The researchers examined data from more than 170,000 people aged 80 to 83 who received the vaccine between December 15 and 20 last year, at the time it was the only vaccine used in the UK. They found that between 35 and 41 days after the first vaccination, emergency admissions were 75% lower in the vaccinated group compared to the unvaccinated 76 to 79 years of age.
George is Digismak’s reported cum editor with 13 years of experience in Journalism