Study shows single dose of AstraZeneca or Pfizer produces powerful immune response

The first study to directly compare immune responses between Pfizer and AstraZeneca coronavirus vaccines found strong and broadly similar antibody responses in people over 80 years of age after receiving the first dose of either form, as one scientist revealed through research published on the Social Science Research Network (SSRN) website.

The British study also found that a critical component of the immune system, known as T cells, showed a greater response in those who received the AstraZeneca vaccine and the University of Oxford than in those who received the Pfizer vaccine and BioNTech.

“We demonstrate a comparable induction of antibody responses with the two vaccines, but higher levels of cellular immunity after the ChAdOx1 vaccine (…) Antibody responses after the two vaccines were generally equivalent, as measured by the Roche and Abbott trials, ”the research notes.

The discovery suggests thate the policy of extending the intervals between the first and second doses for both vaccines, as the UK has done to extend the reach of its vaccination campaign, is secure.

Scientists responsible for the study, who analyzed blood samples from 165 Britons aged 80 to 99 who had received a first dose of the coronavirus vaccine, nevertheless said the finding warrants further investigation.

While antibodies can block the ability of the coronavirus to enter human cells, T cells can act as a broader protection by attacking and killing any cells that have been infected with the virus.

“These vaccines are equivalent and effective in inducing antibody responses in the vast majority of people (in this study), even after a dose,” he explained. Paul moss, professor of hematology at the British University of Birmingham, who co-led the research.

“Both vaccines are good”, highlighted in a presentation on the results of the study.

The researchers also found that immune responses were “markedly improved” by a previous infection with SARS-CoV-2. According to the report, in the entire cohort of 165, evidence of prior natural infection was seen in 8 donors and was associated with a 691 and 4-fold increase in humoral and cellular immune responses.

“We observed a remarkable 691-fold increase in the mean antibody titer after vaccination in participants who had signs of previous infection. This pattern has also been seen in younger people with an average age of 40 before, but at that age the relative increase was only 45 times, indicating a further 15-fold increase in “ preparation. to infection ” in the elderly. Likewise, among health workers, a more modest increase of 6.5 times was observed after the first vaccination in those who had a previous infection ”, detailed the British scientists.

The study was published online as a pre-print of the scientific journal The Lancet before being peer reviewed.

Scientists have discovered that key antibodies were present and at similar levels in 93% of 76 study participants who received the single dose of Pfizer vaccine and in 87% of 89 participants who received AstraZeneca injection.

Helene parry, a clinical professor at the University of Birmingham who co-led the study, said the tests also showed that a higher proportion of those who received the AstraZeneca vaccine had a detectable T-cell response.

This finding adds to other emerging evidence from COVID-19 studies suggesting that antibodies – which prevent the coronavirus from attaching to human cells – may not be the only important building block for immunity, and that T cells can also play an important protective role. .

“We now need to do more research to understand what this difference in T cell responses means.”Parry said.

Almost half of the British population has received at least one dose of the vaccine against the coronavirus, one of the highest inoculation rates in the world. The vast majority have received the formula from Pfizer or AstraZeneca.

For its part, the UK will expand with more volunteers and new types of vaccines a trial to establish the effectiveness of providing two different preparations against COVID-19 in the first and second doses.

The researcher in charge of this program, Matthew Snape, of the University of Oxford, explained on Wednesday that it plans to recruit 1,050 new volunteers over the age of 50 who have already received an injection of the Pfizer or AstraZeneca vaccine after 12 weeks.

They will receive a second dose of the same vaccines or Moderna (already approved) or Novavax preparations, which should obtain approval from the British authorities soon.

The trial, called Com-Cov and which is in charge of the so-called National Consortium for Vaccination Assessment, began last February with the participation of some 800 volunteers over the age of 50 living in England.

To this first group The Oxford / AstraZeneca preparation was administered followed by the Pfizer / BioNTech preparation and vice versa, with a period between the two of 12 weeks.

Experts want to analyze the possibility that the vaccine combination provides broader and more lasting immunity against the coronavirus and its new variants, which, moreover, would make the vaccination campaign more flexible in the face of possible supply problems.

Com-Cov plans to present preliminary results from the first phase next month, while those from this expanded second phase could be available in June or July, although both trials last around 13 months.

“If we can show that this mixed process generates an immune response as good as the standard process, without significantly increasing reactions to the vaccine, it will allow more people to complete their COVID-19 vaccination cycle faster.”Snape showed the chain BBC.

The best case scenario, he said, is that “we don’t have to rule out” one of the possible vaccine combinations. “That’s the goal, to see if there’s a combination that we shouldn’t come up with because it doesn’t generate a good immune response. I hope that will not happen, ”added the expert.

To date, more than 32 million people have received the first dose of a covid vaccine in the UK, while 7.8 million are already immune with the two bites.

Apart from this Com-Cov trial, authorities have indicated that, for now, citizens will continue to receive the same type of preparation throughout the cycle, although another brand can be administered if it is not. available, as recommended by the Joint Committee on Immunization (JCVI).

The full study

With information from Reuters and EFE

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