Researchers have reacted with skepticism to claims by AstraZeneca’s CEO that low uptake of Oxford / AstraZeneca jab among older Europeans could explain the current rise in Covid-19 infections on mainland Europe.
Pascal Soriot told BBC Radio 4’s Today program that differences in T cell immunity between vaccines could mean that those who received the Oxford / AstraZeneca jab had prolonged immune protection against the virus. T cells are a class of immune cells that train antibody-producing B cells about the nature of the viral threat and directly kill infected cells.
Soriot said: “It’s really interesting when you look at the UK. There was a huge peak of infections, but not so many hospitalizations compared to Europe. In the UK [the Oxford/AstraZeneca] Vaccine was used to vaccinate older people, whereas in Europe it was thought that the vaccine initially did not work on older people.
“What I’m saying is that T cells matter, and it’s particularly related to the shelf life of the response, especially in older people, and this vaccine has been shown to stimulate T cells to a greater extent in older people. There is no evidence of anything… we do not know. But we need more data to analyze this and get the answer. “
Germany was the first European country to recommend not giving AstraZeneca plugs to people over 65 at the end of January, citing a lack of efficacy data for the vaccine in this age group. Other European countries quickly followed suit with similar recommendations, including Italy, France, Poland and Sweden, although many later changed this guide following the publication of additional impact data.
Some even even said that it should only be used in older age groups after the European Medicines Agency (EMA) reported a possible link between the vaccine and very rare cases of blood clots. Possibly as a result of these mixed messages, many Europeans were initially reluctant to receive jab.
There are theoretical reasons why the AstraZeneca vaccine may elicit slightly different immune responses compared to an mRNA-based vaccine, such as Pfizer jab. Both equip the cells with the genetic instructions to make the coronavirus tip protein, but the AstraZeneca vaccine does so using a modified virus to which the immune system may also respond.
Deborah Dunn-Walters, chair of the British Society for Immunology’s Covid-19 task force and professor of immunology at the University of Surrey, said: “It’s a slightly more complicated delivery system, so you can expect differences – but try to explain them. differences would require a lot of research. “
Danny Altmann, professor of immunology at Imperial College London, said it would be “foolhardy” to try to attribute the differences in the shape of individual countries’ infection curves to a single factor. “I do not know where you would start doing it scientifically,” he said. “All the vaccines are quite amazing in varying degrees. They all induce the full spectrum of immunity, including neutralizing antibodies and [different types of] T cells. “
Professor Matthew Snape, from the University of Oxford, has compared antibody and T cell responses in humans receiving standard or mixed regimens for the Pfizer and AstraZeneca vaccines. Although his team found evidence that a single dose of AstraZeneca induced a better T cell response, the response was very similar shortly after receiving two doses. “Excitingly, the best T cell responses seem to come if you give a first dose of the AstraZeneca vaccine followed by Pfizer,” he said.
Finding ways to optimize the immune response to Covid-19 vaccines is an ongoing focus of research, and Snape is following up on these studies to see how humans’ immune response takes shape in the long run.
Understanding the differences between countries’ rates of infection and hospitalization is further complicated by factors such as when Covid-19 restrictions were lifted, and the degree of variability in the difference between the first and second doses, the age of the population and the incidence of other diseases, and the prevalence of New varieties, especially if they appear long after people have been vaccinated.
“Drawing comparisons between countries presents many difficulties and will very likely lead to unreliable conclusions,” said Dr Lance Turtle, a senior clinical associate professor and chief physician in infectious diseases at the University of Liverpool.
Earlier, a former chair of the British Vaccine Task Force, Dame Kate Bingham, called on the government to do better in its preparations for future disease outbreaks. She wrote in the Times, saying Whitehall’s machinery was “dominated by process rather than result, causing delay and inertia”, adding that the jab rollout would have been delayed if it had been left to the normal operation of government.