There is no evidence yet to support dishing out Covid booster vaccines to the entire population, a major scientific review has concluded.
Experts writing in the Lancet admitted there may be ‘some gain’ from administering top-up jabs.
But they insisted protection from two doses is so high — including against the more infectious Delta strain — that they are not currently routinely needed.
They said extra jabs should be given to the unvaccinated, in a call to arms to jab the third-world which is lagging behind in the global roll-out.
Boris Johnson is expected to finally set out Britain’s approach to Covid booster jabs tomorrow, when he unveils his virus-fighting plans for this winter.
Israel has already dished out third doses, which scientists say stopped the onslaught of Delta and the country’s fourth wave. It prompted calls for the UK to follow suit.
The graphs shows the data the researchers considered when penning their advice against a widespread booster campaign, because ‘vaccines continue to be effective against severe disease’. Each graph displays the vaccines’ effectiveness against severe disease (y axis) and against any infection (x axis). The top left graph (A) shows the overall rate of effectiveness, while the top right graph (B) shows how well the jabs work against different strains. This shows the injections are more than 90 per cent protection against severe disease for Delta, Alpha and Beta, and more than 80 per cent protection against any infection from Alpha and Delta. The bottom left graph (C) shows how effective different types of vaccines are, with vector jabs — such as AstraZeneca and Janssen — being more than 90 per cent effective against severe disease and more than 70 per cent effective against infection. Meanwhile, mRNA jabs — such as Pfizer and Moderna — are around 95 per cent effective against serious illness and any infection. The bottom right graph (D) plots the efficacy of vaccines soon after vaccination compared to later. Over time, the protection against infection drops by around 10 per cent, while protection against severe disease remains high at over 90 per cent
In a report today, scientists warned against a mass rollout of booster vaccines and said the doses should go to poorer countries where rollouts have been slow
A team of international experts, including Oxford University epidemiologist Richard Peto, as well as officials from the World Health Organization and US Food and Drug Administration, looked at the available evidence from randomised controlled trials and observational studies published in peer-reviewed journals and pre-print servers.
The observational studies revealed vaccines were still highly effective against severe disease, including that from all the main variants of the virus.
Vaccines were up to 95 per cent effective at stopping severe disease, though some protection against infection has faded over time.
The vaccines were found to be less effective against asymptomatic disease and transmission than against severe disease.
But even in populations with high vaccine coverage the unvaccinated minority are still the major drivers of transmission and are at the highest risk of serious disease, experts said.
And the team noted that even if antibody protection wanes over time, this does not necessarily mean protection against serious illness from the virus will also drop.
Antibody responses can be ‘relatively short lived’, but other markers of protection — including memory responses and cell-mediated immunity — are longer-lived, they said.
Dr Ana-Maria Henao-Restrepo, an expert in vaccines at the WHO and lead author of the review, said: ‘Taken as a whole, the currently available studies do not provide credible evidence of substantially declining protection against severe disease, which is the primary goal of vaccination.
‘The limited supply of these vaccines will save the most lives if made available to people who are at appreciable risk of serious disease and have not yet received any vaccine.
‘Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated.
‘If vaccines are deployed where they would do the most good, they could hasten the end of the pandemic by inhibiting further evolution of variants.’
The experts say that if boosters are used, there will be a need to identify specific circumstances where the benefits outweigh the risks.
Countries will see more breakthrough cases as the vaccine roll-out continues, but evidence suggests the virus has not yet evolved to the point at which it is likely to escape the immune response induced by any of the vaccines.
The researchers suggest that even if new variants evolve that can escape the current vaccines, they are most likely to do so from strains that have already become widely prevalent.
Therefore, the effectiveness of boosters developed specifically to match potential newer variants could be greater and longer lived than boosters using current vaccines.
The article states there should be ‘careful and public scrutiny’ of booster data to make sure decisions are informed by ‘reliable science more than by politics’.
Co-author Dr Soumya Swaminathan, WHO chief scientist, said: ‘The vaccines that are currently available are safe, effective, and save lives.
‘Although the idea of further reducing the number of Covid cases by enhancing immunity in vaccinated people is appealing, any decision to do so should be evidence-based and consider the benefits and risks for individuals and society.
‘These high-stakes decisions should be based on robust evidence and international scientific discussion.’
It comes as Boris Johnson is expected to set out the UK’s booster plans tomorrow.
In June, the Joint Committee on Vaccination and Immunisation (JCVI), which advises the Government on the rollout, published interim guidance on who should be prioritised for booster jabs.
It warned its guidance could change substantially, but under the initial plans, a first wave of booster jabs would be given to people who are immunosuppressed and clinically extremely vulnerable, over-70s, those in care homes and frontline health and social workers.
In a second stage, over-50s, those in a flu or Covid risk group, and those living with immunosuppressed people would be eligible.
But the JCVI is now expected to reveal a watered down version of these plans, with jabs going to the most vulnerable.
It comes after Covid cases fell sharply in Israel last week following a third wave of infections, while hospitalisations and deaths were also trending downwards.
Israeli scientists pinned the fall on booster doses, which it began dishing out to over-60s in July, before offering them to everyone over-12 at the end of August.
Professor Azra Ghani, chair of infectious disease epidemiology at Imperial College London, said the paper presents a ‘very thorough review’ of studies on the effectiveness of the Covid jabs.
But it is also important to consider other factors the researchers did not examine, he said.
Professor Ghani said: ‘Whilst it is clear that the effectiveness of current vaccines against severe disease has only slightly reduced with the emergence of the Delta variant, there has been a significant reduction in their effectiveness against infection.’
And there is emerging evidence of waning of efficacy against both infection and disease, he said.
Professor Ghani said: ‘These reductions may appear to be numerically small.
‘But it is important to bear in mind that when applied across a population, even a reduction from 95 per cent to 90 per cent can result in a substantial increase in cases requiring hospitalisation in the absence of other non-pharmaceutical interventions.
‘Similarly a reduction in vaccine efficacy against infection will substantially increase transmission and hence the risk to both vaccinated and unvaccinated individuals.
‘Even in the most developed countries, these small differences can put a severe strain on the health system.
‘There is therefore no ‘one size fits all’ approach to booster vaccines as implied here, nor should such a strategy be described as ‘high-stakes’.
‘As the authors conclude, countries should use current best evidence to assess their benefits. As part of this evaluation, it is important that both the direct and indirect impact of the proposed vaccination strategy is captured.’