Scientists have published the first real data from Africa on the effectiveness of two doses of vaccination AstraZeneca / ChaAd0x-1 COVID-19, which show that, although protective against SARS-CoV-2, immunity against delta and omicron variants was lower, even in the context of previous infection or infection after vaccination.
In a preliminary press not yet peer-reviewed, researchers from Nigeria and the UK analyzed data from 140 health workers from the Nigerian Institute for Medical Research and the Federal Medical Center Ebut Meta and two private hospitals in Lagos. All participants received two doses of AstraZeneca vaccine is introduced in the period from January to July 2021, between receptions of 12 weeks.
According to the World Health Organization, about two-thirds of people in Africa are estimated to have been exposed to SARS-CoV-2, the virus that causes COVID-19, and more than 250,000 deaths. However, since the introduction of the AstraZeneca vaccine against COVID-19 in mid-2021, no real data on its effectiveness have been available.
The spread of the vaccine on the African continent was mixed: less than one in six (16%) of the eligible population received both doses, and only about one in 75 (1.3%) received a booster dose.
The team tested participants looking for evidence of antibodies in individuals who had previously been infected and not in those who had been raised as a result of the vaccine. Initially, they found that 62 participants gave a positive result (44%).
In a subset of 49, they then tested serum samples taken from volunteers for pseudoviruses – synthetic viruses that mimic the behavior of SARS-CoV-2 and its variants, but which are safe to study in the lab – to see if vaccinated people were able to vaccinate it for humans. .
The team found that on average one month after vaccination, delta and omicron variants required a 4.7- and 9.6-fold increase in serum antibody concentrations to neutralize the virus compared to the “wild-type” virus (original strain). This suggests probable poor protection against omicron variant infection despite two doses of vaccine and infection before or during the study.
To look for evidence of a vaccine breakthrough – if the virus is capable of infecting vaccinated individuals – the team looked at those people who had no signs of previous infection and found that 14% became infected between one and three months after vaccination. This occurred during the delta wave, and participants demonstrated excellent immunity against delta, but consistently suboptimal immunity to the omicron.
Dr Adam Abdullahi, a researcher at Cambridge and Africa from the Institute of Human Virology, Abuja, Nigeria, and Cambridge University, said: “Although the vaccine is the most common, there has been very little information so far about how effective the AstraZeneca vaccine protects people in Africa from omicron and even from infection levels before and after vaccination using accurate laboratory tests.
“In our study among health professionals in Nigeria, we found that almost 50% were infected before the first dose of the vaccine in early 2021. ”
Professor Babatunde Laval Salako, director of the Nigerian Institute for Medical Research in Lagos, said: “The good news was that the AstraZeneca vaccine was effective in protecting people from the virus, at least initially. But with the advent of deltas and omicron variants, we began to notice that the ability to neutralize viruses declines, and almost one in five people who received two doses was infected within three months of vaccination. severe illness in those who have a depressed immune system or who are medically vulnerable. ”
Professor Ravi Gupta, a lead researcher at the Cambridge Institute for Therapeutic Immunology and Infectious Diseases at Cambridge University, added: “Given recent evidence that a third“ booster ”dose of mRNA vaccine increases and expands protection against amicron, we urgently need more long-term follow-up research in West Africa, including booster dose trials. If we are going to control it viruswe will do so only by ensuring that everyone who is entitled is protected from current and future options that may be more pathogenic and difficult. ”
Adam Abdullah et al., Antibody response to AZD1222 vaccination in West Africa (2022). DOI: 10.1101 / 2022.05.04.22274668
Citation: The first real data from Africa on the immune response to the vaccine against COVID-19 AZ / Oxford (2022, May 11), obtained May 11, 2022 from https://medicalxpress.com/news/2022-05-real- world-africa-immune-response-azoxford.html
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