Covid-19: epidemiologists fear that first batch of vaccines will lose effectiveness

Covid-19: epidemiologists fear that first batch of vaccines will lose effectiveness
Covid-19: epidemiologists fear that first batch of vaccines will lose effectiveness
For 88% of respondents, there is a risk that low vaccination coverage will cause immunizers to stop working against the strains of Sars-CoV-2 that are emerging. Photo: Pascal Guyot / AFP

A survey of 77 epidemiologists from 28 countries – Brazil was left out – found that, for 88% of them, low immunization coverage, especially in developing countries, can render vaccines for Covid-19 harmless. The fear of experts is that, when reaching the large part of the population, most substances are no longer suitable for new variants that may arise.

Conducted by a number of non-governmental organizations, such as Amnesty International and Oxfam, the survey also shows that two-thirds of respondents believe that first-generation vaccines should have an average effect of nine months. Until now, the main laboratories producing immunizations, such as Pfizer, Moderna, AstraZeneca and Sinovac, have stated that their products work with the variants that are now dominant: from England, South Africa and Brazil. Pharmaceutical companies have also expressed their opinion on the feasibility of adapting vaccines annually, as is the case with influenza. Experts interviewed by the so-called Popular Alliance of Vaccine, which conducted the research, said they believed that these changes would be necessary for the immunizers to continue working.

Concerned about the slowness in vaccination coverage, the coalition warns in the report that, at the current rate, “it is likely that only 10% of people in most poor countries will be vaccinated by next year.” “The more the virus circulates, the more likely it is that mutations and variants will appear, which could render our current vaccines ineffective. At the same time, poor countries are being left behind without vaccines and basic medical supplies, such as oxygen. As we’ve learned, viruses don’t care about borders. We have to vaccinate as many people as possible around the world, as soon as possible. Why wait and watch instead of anticipating it? ”Asks Devi Sridhar, professor of global public health at the University of Edinburgh.

Gregg Gonsalves, a professor at Yale University heard about the research, stressed that interest in broad coverage should be worldwide. “With millions of people around the world infected with this virus, new mutations are emerging every day. Sometimes, they find a niche that makes them more suitable than their predecessors, ”said Gonsalves, who preferred not to stipulate an expiration date for first-generation vaccines. “These lucky variants could transmit more efficiently and potentially evade immune responses to previous strains. Unless we vaccinate the world, we leave the field open to more and more mutations, which can produce variants that can escape our current vaccines and require booster doses to deal with them. ”

The coalition said in a statement that wealthy nations are hindering the fair division of immunizers. “The defense of rich countries against the monopolies of pharmaceutical giants means that global supplies are being artificially rationed, with a handful of companies deciding who lives and who dies. Earlier this month, wealthy countries blocked a proposal to waive Covid-19 vaccine intellectual property rights. The alliance urges them to reconsider when negotiations resume at the World Trade Organization in April, ”he says.

High circulation

Jan Felix Drexler, a researcher at the Instituto de Virología Charitè in Berlin and author of a recent study on the mutation of Sars-CoV-2, explains that as long as the numbers of infections remain high, the virus will continue to change. According to Drexler, the causer of Covid-19 has a mutation rate that is much lower than that of influenza, but higher than that of other coronaviruses. This happens precisely due to the high circulation of the microorganism.

“Based on the rates of evolution seen in endemic coronaviruses of the common cold, we expect Sars-CoV-2 to begin to change more slowly when infections begin to subside – that is, once a large proportion of the global population has developed immunity as a result of infection or vaccination, ”says Drexler, who did not participate in the Alliance’s research. “Covid-19 vaccines will need to be monitored regularly throughout the pandemic and updated when necessary. Once the situation stabilizes, vaccines are likely to remain effective for longer. ”

Active defenses

At the same time, a scientific study released yesterday by researchers at the US National Institute of Allergies and Infectious Diseases (Niaid) and the Johns Hopkins School of Medicine suggests that the variants may not affect the response of first-generation vaccines. The scientists analyzed blood samples from 30 former Covid-19 patients, who recovered before the new strains appeared, and found that cells called CD8 + T – which kill infected ones, preventing the organism’s infection cycle – remained. active against Sars-CoV-2.

In tests with the volunteers’ cells, the scientists noted that CD8 T was able to recognize the main circulating variants (United Kingdom, South Africa and Brazil). Mutations in the viral protein spike made it difficult to detect Sars-CoV-2 by neutralizing antibodies, but did not prevent this cell group from recognizing infected cells and attacking them. The researchers said that larger studies are needed, but said that the results obtained in this analysis suggest that the cellular response in people who have recovered from the disease – and, more likely, in those vaccinated – is not affected by new strains.

The day after a report by the World Health Organization (WHO) states that the chance that Sars-CoV-2 arose from the accidental escape of the virus from a Chinese laboratory is very low, the director-general of the United Nations agency United, Tedros Adhanom Ghebreyesus, gave a statement that generated immediate global reaction. At a press conference at which he officially presented the document, he called for this possibility to be investigated again. “This requires more investigations, probably with new missions with experts, which I am willing to deploy,” said Ghebreyesus, who also criticized the fact that experts were unable to access much data during the special mission in China in January and February. .

The United States and 13 other countries expressed “common concerns” in a joint statement on the report. “It is essential to express our common concerns that the study by international experts on the origin of the Sars-CoV-2 virus has been significantly delayed and (that the team) has not had exhaustive access to the original data and samples,” said the US government with others countries, including the United Kingdom, Israel, Canada, Japan, Australia, Denmark and Norway.

Three hypotheses

In the official presentation of the report on the origin of the virus, the head of the organization said that the investigation made it possible to advance the topic “in an important way”, but it generated “other questions that need further studies”. The work favors the widely accepted theory of the natural transmission of the virus from a reservoir animal (probably the bat) to humans through another animal that has not yet been identified.

The direct transmission of the virus through a reservoir animal is considered “possible to probable” by experts, who also do not rule out the possibility that the contagion occurred through frozen meat – a track defended by Beijing -, considering this “possible” scenario. The report recommends continuing studies on the basis of these three hypotheses, but neglects the possibility of transmission to humans during a laboratory accident, contrary to the statements of the Director-General of WHO.

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