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Delaying doses of coronavirus inoculations will increase the chances of emergence of a vaccine-resistant strain of Covid-19, government scientists have warned.
In new reports, released by the Scientific Advisory Group for Emergencies (Sage), experts also warned that the new resistant variants were a “realistic possibility” motivated by the virus responding to increasing levels of natural immunity among the population. .
The government’s decision to postpone the second dose of the vaccine to 12 weeks instead of three, in an attempt to protect more people from the virus, has angered frontline health workers who fear they may be at risk increased infections.
There have also been suggestions from Israel, which have not yet been fully validated, that protection against a first dose may be much less than initially thought.
In papers published Friday, Sage scientists found an “increased risk of virus replication under partial immunity after one dose only after two doses, so in the short term, postponing the second dose should somewhat increase the likelihood of emergence of the vaccine. resistance – but probably from a low base.
“Is such an increase material? It is currently not possible to quantify the likelihood of vaccine resistance developing due to the delay of the second dose, but it is probably low. The UK currently has over 1,000 deaths linked to Covid-19 every day and has limited stocks of vaccines.
‘Under current UK circumstances, the unquantifiable but probably low probability that the second delayed dose will generate an escape mutant of the vaccine must be weighed against the measurable benefits of doubling the rate at which the most vulnerable can benefit. protection induced by the vaccine. ”
But the article adds: “Given what we have observed recently with the B.1.1.7 and B1.351 variants, it is realistic to think that over time immune leakage variants will emerge, possibly in due to increased immunity of the population following natural infection. ”
He warned: “The effectiveness of the vaccine after a dose should be closely monitored to inform future vaccine policy.”
Sir Patrick Vallance, the chief scientific adviser, told a press conference in Downing Street on Friday that the virus was likely to exist “forever”, adding: “The riskiest thing in terms of a new mutation is to have a very high prevalence. The more the virus is transmitted and replicated between people, the more likely it is to get a mutation, and that is what is happening around the world. This is the biggest risk.
“There is always a risk if you start having partial immunity, but there is also a benefit which is that partial immunity can actually stop the infection faster.
Chris Whitty, the government’s chief medical adviser, said: “All medicine is about balancing risks. Our general view was that the balance of risk was firmly in favor at this point in the UK outbreak of having many more people vaccinated, but that means a delay. That particular risk was a much lower risk of not having people vaccinated, which was the alternative.
All viruses mutate and natural variations of the Sars-CoV-2 virus have been identified around the world and the Sage article said this would likely happen at a “faster rate” as more people became immune after infection.
He added: “Most mutations will be inconsequential, but a few can, by chance, confer a functional advantage over others and, through natural selection, become dominant variants generated in the laboratory.
He said there was “theoretical and experimental data supporting the possibility” that the virus could generate new variants that “escape” antibody therapies, convalescent plasma and vaccines as well as natural immunity.
The newspaper said vaccinated people who developed Covid-19 must have their virus genetically sequenced “as quickly as possible to understand whether viral variation can account for the breakthrough.”
Increased sequencing of tests would help identify new clusters and spot changes as they appear after vaccine deployment.
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