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According to a new UK study, people who receive a shot of the Covid-19 vaccine and who have never been infected with the virus could be very vulnerable to new variants.
Researchers at Imperial College London, Queen Mary University of London and University College London examined the immune responses of healthcare workers who had received a BioNTech / Pfizer vaccine.
The scientists found that they showed people who had not previously been infected with Covid-19 very low levels of neutralizing antibodies against the original Wuhan strain, variant B.1.1.7 first identified in Kent and B.1.351 from South Africa.
In contrast, those who had previously had a mild or asymptomatic infection and then received a single dose appeared to have greatly improved protection against both B.1.1.7 and B.1.351, demonstrating elevated neutralizing antibodies and a strong cell response. T cells, reminiscent of past infection.
A dose without previous infection “seems very weak, especially against new variants,” said Danny Altmann, a professor of immunology at Imperial. “Our message would stay there until you get your second dose.”
But, Altmann added, the previous infection along with a single shot of the vaccine provoked a “great reaction.” “A previous infection rescues your response against variants,” he said.
The Imperial paper was published shortly after the first detailed study of the “vaccine failure” in the UK, commissioned by the government’s Scientific Advisory Group (Sage), which found that more than 500 elderly people were developing symptoms. of Covid-19 severe enough to be hospitalized at least three weeks after vaccination, of which 113 died later.
Sage research, conducted by the Isaric Coronavirus Clinical Characterization Consortium, analyzed 52,280 hospitalized patients as of December 8, when vaccine deployment began in the UK.
Patients who had been vaccinated more than three weeks earlier and who should have benefited from immune protection against Covid-19 accounted for 1% of the hospitalized sample. About one-fifth of this group died from the disease.
Professor Calum Semple of the University of Liverpool, co-leader Isaric, said: “These are real-world data showing that vaccines work, but it is not expected to show any vaccine failure, especially in the fragile elderly population “.
He added that the absolute numbers of people dying this way were “very small” compared to the total vaccinated population.
Researchers say the general findings show that vaccination greatly reduces the risk of hospitalization and death, according to the results of clinical trials, although the design of their study does not allow them to calculate an efficacy figure. of vaccines.
The U.S. Centers for Disease Control published a paper detailed controlled case study this week of 417 patients in 24 hospitals, who found that BioNTech / Pfizer and Moderna vaccines were 94% effective in preventing hospitalization after two doses and 64% after one dose. Most people in the Isaric study in the UK had only received the first dose of Pfizer or Oxford / AstraZeneca vaccine.
The CDC is also conducting a broader survey of what he calls “advanced vaccine cases” of Covid-19 in the U.S. As of April 20, it had received 7,157 reports of infections in fully vaccinated people, including 498 hospitalizations and 88 deaths.
“Advanced vaccination cases reported will account for an insufficient number,” the CDC said, because the data is incomplete and depends on voluntary reports. “No vaccine is 100% effective in preventing disease. There will be a small percentage of people who are fully vaccinated who still get sick, are hospitalized, or die of Covid-19.”
Semple made the same point about Isaric research. “We believe this is a story about the success of the vaccine, but within a wider society there are suspicions of vaccine data,” he said, adding that the study responded to “the feeling of some that we didn’t look at enough with the vaccine failure ”.
Dr. Annemarie Docherty of the University of Edinburgh, co-author of the Isaric study, said: “We are talking about statistics, but if it is your grandmother who was vaccinated and later died with Covid, it is a personal tragedy. “.
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