US criticised for rolling out Covid boosters without human trials

Health experts have warned that the US decision to roll out new Covid boosters without clinical testing on humans risks denting public trust and increasing hesitancy about vaccines.

The Joe Biden administration is using the bivalent boosters, which contain the original Covid strain and the genetic code of the Omicron sub-variants BA4 and BA5, to vaccinate more Americans against the virus.

It has bought 171mn doses of the BioNTech/Pfizer and Moderna boosters for $5bn and fast-tracked their authorisation before human trials are complete, hoping that they provide better protection against the dominant variants than existing Covid vaccines.

As doses began arriving at pharmacists for distribution this week US officials said the rollout marked an “important milestone”. In the future people would probably only require annual boosters just as they take a yearly influenza jab, they said.

But several health experts note that the boosters have yielded only limited data from a small number of tests on mice. They say there is no evidence that they provide better protection against infection or severe disease than existing jabs.

“Without the data and getting a human response in at least a limited number of people you just set it up for the anti-vaxxers, anti-science [people],” said Eric Topol, founder and director of the Scripps Research Translational Institute.

“There are already groups calling it the mouse vaccine . . . We already have a trust problem in this country and we don’t need to make it worse,” he said.

The US approach diverges with that of the EU, where regulators have said they want to review clinical data before authorising the latest generation of bivalent boosters.

Last month the UK became the first country to approve a bivalent booster. But it waited for clinical data to greenlight a shot targeting the original Covid strain and the BA1 sub-variant, which has since been superseded by BA4/BA5.

Experts say vaccine hesitancy is just one of several challenges facing the US booster campaign and have urged caution in prematurely declaring victory over the virus.

Two and half years into the pandemic there is growing public complacency towards Covid, as most people have already contracted the virus and been vaccinated. The Biden administration has also failed to secure $22.4bn additional funding from Congress, which could restrict its ability to replenish vaccine supplies.

“People have booster fatigue. They feel by this stage they are mostly protected and the pandemic is largely behind them: so I think there will be less interest in these boosters,” said Paul Offit, director of the Vaccine Education Centre at Children’s Hospital of Philadelphia.

Offit was one of two members of a US Food and Drug Administration advisory panel to vote against asking Pfizer and Moderna to develop the bivalent vaccine without clinical data showing it performed better than the existing Covid jab.

“What bothers me in this is that we’re willing to move forward with a vaccine with no human data? I just think that’s a lot to ask people,” he told the Financial Times.

Vaccination and booster rates in the US already lag other developed countries with two-thirds of Americans receiving two Covid jabs and only a third of the population boosted. The comparable figures in France are 83 per cent and 65 per cent.

Health experts say the modest vaccination rate in the US is one of the main reasons it has recorded more deaths from Covid than any other country — 1.04mn. The virus continues to kill about 350 people per day, according to the Centers for Disease Control and Prevention, and yet the number of Americans seeking boosters has fallen sharply this year.

Authorities say the threat posed by waning immunity from vaccination and the potential for a fresh wave of infections in autumn justify its decision to roll out bivalent boosters without clinical data.

They argue that by tailoring the jab to target BA4/BA5, sub-variants which account for more than 90 per cent of infections, as well as the original Covid strain, it should boost immunity and do a better job in blocking infections. The vaccine is so similar to the existing Covid jab and a separate bivalent jab targeting the BA1 variant, which has undergone trials, there is no need to wait for results in ongoing human trials, they say.

Some scientists agree, noting that new clinical data is not always required when the influenza jab is tweaked annually to target the latest strains.

Nancy Jecker, professor at University of Washington School of Medicine, said the risk of approving the boosters was minimal given they are not significantly different to the original Covid jabs.

“Emergency authorising Moderna and Pfizer boosters based on animal studies gives people the chance to minimise their risk of Covid as more people congregate indoors during fall and winter months,” said Jecker.

But Topol and Offit argue the US should have waited for evidence the boosters are better than the existing jabs.

“I don’t think they have proven that this influenza vaccine strategy — where we pick influenza strains every March for a vaccine that comes out in September — makes sense for Covid,” said Offit.

He said there is no evidence showing the BA4/BA5 booster provided better protection than existing jabs. Initial clinical data for the BA1 bivalent booster showed it produced virus fighting antibody levels that were 1.5 to 1.75 fold higher than the existing jab, which was not a clinically significant difference, Offit said.

The CDC cites polling which suggests 72 per cent of respondents would definitely or probably receive bivalent boosters. If uptake of the jabs reach similar levels to the annual flu vaccine — half of US adults — by early autumn CDC modelling predicts it would prevent 100,000 hospitalisations, save 9,000 lives and billions of dollars in healthcare costs.

To boost uptake the CDC has simplified its guidance on eligibility, recommending a single bivalent booster for everyone over 12 years of age who has already received a Covid vaccine.

But workers on the frontline of the inoculation drive are sceptical the public will rush to get another jab.

“I think demand will continue to be sporadic because those people who want to be vaccinated have already got the vaccine and been boosted,” said Rene Rodriguez, owner of Tens Pharmacy in Roseland, a small town in New Jersey.

“There are really two types of people: those who believe in the vaccine, who are generally up to date with their jabs and those that don’t.”