WHO panel backs use of vaccine modified to target Omicron

GENEVA • A modified coronavirus vaccine that targets the Omicron variant can be administered as a booster dose to broaden immunity, a technical advisory group set up by the World Health Organisation (WHO) has said.

Such a variant-adapted vaccine may benefit those who have already received the primary series of shots, the agency's panel on Covid-19 Vaccine Composition said on Friday, citing available data.

The vaccines could be considered for use globally by the agency once they get emergency use authorisation or an approval by a stringent national regulatory authority.

Vaccine makers including Moderna and Pfizer are developing a potential next-generation booster targeted at both the Omicron variant as well as the original strain of the coronavirus.

Moderna last week said a new version of its vaccine produced a better immune response against Omicron than the original shot, while the European Medicines Agency last week began rolling reviews of the variant-adapted Covid-19 vaccines from Moderna and Pfizer.

Meanwhile, new findings suggest that people infected with the earliest version of the Omicron variant of the coronavirus, first identified in South Africa in November, may be vulnerable to reinfection with later versions of Omicron even if they have been vaccinated and received booster shots.

Vaccinated patients with Omicron BA.1 breakthrough infections developed antibodies that could neutralise that virus plus the original Sars-CoV-2 virus, but the Omicron sublineages circulating now have mutations that allow them to evade those antibodies, researchers from China reported on Friday in Nature.

Omicron BA.2.12.1, which is at present causing most infections in the United States, and Omicron BA.5 and BA.4, which now account for more than 21 per cent of new US cases, contain mutations not present in the BA.1 and BA.2 versions of Omicron.

Those newer sublineages "notably evade the neutralising antibodies elicited by Sars-CoV-2 infection and vaccination", the researchers found in test-tube experiments.

The monoclonal antibody drugs bebtelovimab from Eli Lilly and cilgavimab, a component of AstraZeneca's Evusheld, can still effectively neutralise BA.2.12.1 and BA.4/BA.5, the experiments also showed.

But vaccine boosters based on the BA.1 virus, such as those in development by Pfizer-BioNTech and Moderna, "may not achieve broad-spectrum protection against new Omicron variants", the researchers warned.

Previous research that has not yet undergone peer review has suggested that unvaccinated people infected with Omicron are unlikely to develop immune responses that will protect them against other variants of the coronavirus.

"My personal bias is that while there may be some advantage to having an Omicron-specific vaccine, I think it will be of marginal benefit over staying current with the existing vaccines and boosters," said Dr Onyema Ogbuagu, an infectious diseases researcher at Yale School of Medicine in New Haven, Connecticut, who was not involved in the new study.

"Despite immune evasion, the expectation can be that vaccines will still protect against serious disease," Dr Ogbuagu said. "If you're due for a booster, get a booster. What we've learnt clinically is that it's most important to stay up to date with vaccines" to maintain high levels of Covid-19 antibodies circulating in the blood, he added.

Dr Adolfo Garcia-Sastre, a microbiology and infectious diseases researcher at the Icahn School of Medicine at Mount Sinai in New York City, suggested that better protection might be seen with vaccines that target multiple strains of the virus or with intranasal vaccines that would increase protection from infection and transmission by generating immunity in the lining of the nose, where the virus first enters.

REUTERS