LONDON – As some governments and pharmaceutical officials brace for COVID-19 booster injections targeting more infectious viral variants, health officials say it is too early to say whether they will be needed.

“We don’t have the information to make a recommendation on whether or not a recall is necessary,” Soumya Swaminathan, chief scientist of the World Health Organization, said in an interview with Zoom on Friday. “Science is always evolving”.

Such a call is “premature” as high-risk individuals in most countries of the world have yet to complete a first round of immunization, Swaminathan said. Data from countries introducing additional precautionary inoculations later this year – particularly for vulnerable people whose immunity to SARS-CoV-2 could decline more rapidly – will inform WHO guidance, he said. she declared.

COVID-19 booster injections are likely to be rolled out in the UK in the fall to prevent another winter surge. Seven different vaccines are being tested on volunteers in England in the world’s first booster study, Health Secretary Matt Hancock said last month.

The UK, which has inoculated a greater proportion of people than any other major economy, has been forced to delay the planned lifting of coronavirus restrictions amid a resurgence of cases caused by the delta variant. The strain, first reported in India, is the most infectious reported to date.

More transmissible variants, including the beta strain that emerged in South Africa, require higher levels of antibodies to prevent infection, prompting vaccine makers, including Pfizer Inc. and Moderna Inc., to to test whether modified versions of their existing vaccines will offer broader immunity.

A dose of the vaccine directed against a variant of Novavax Inc. may provide sufficient protection against the beta strain in people previously immune to COVID-19, according to preclinical research published this month by scientists at the Gaithersburg-based company, Maryland and the University of Maryland School of Medicine.

The modified vaccine also has the potential to provide broad protection against various strains if used as a primary vaccine regimen, Gregory M. Glenn, president of research and development at Novavax, said in a June 11 statement.

So far, existing vaccines approved by the United States work well enough to protect against beta, delta and two other strains that the WHO has designated as variants of concern, said Francis Collins, director of the National Institutes of Health. .

“No one is saying you need a booster today,” Collins said in an interview with biologist Lee Hood at the Precision Medicine World Conference Thursday. “But the boosters could very well be in our future at some point, and they could be there sooner if other variants emerge” that are not as well covered by existing vaccines.

At a minimum, the vaccines should protect against hospitalization, ICU admission and death, according to Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia. “With that bar, we would probably need a vaccine maybe every three to five years,” he said in a STAT biotech podcast Thursday.

Vaccination with a combination of vaccinations may offer longer immunity or fewer side effects for some people, Offit said.

Early data from the UK, Spain and Germany suggests that a “mix-and-match” diet using two different types of vaccines generates more pain, fever, and other minor side effects. compared to two doses of the same inoculation, said WHO’s Swaminathan.

Yet the so-called heterologous prime-boost combinations appear to stimulate a more robust immune response, leading to higher levels of virus-blocking antibodies and white blood cells that kill cells infected with the virus, she said.

Combinations of AstraZeneca Plc and Pfizer-BioNTech injections are being considered in Malaysia, where the government is trying to speed up vaccinations to achieve population-level immunity by the end of the year, the government said on Wednesday. Minister of Science, Technology and Innovation, Khairy Jamaluddin.

“It seems to work well, this heterologous prime-boost concept,” Swaminathan said. “This opens up the possibility for countries that have vaccinated people with a vaccine and are now waiting for the second dose that they are short of, to potentially be able to use a different platform vaccine. “