Too early to tell if Covid-19 booster shots targeting more-infectious variants will be needed: WHO

GENEVA (BLOOMBERG) – As some governments and pharmaceutical officials prepare for Covid-19 booster shots targeting more-infectious virus variants, the health authorities say it is too early to tell if they will be required.

“We do not have the information that’s necessary to make the recommendation on whether or not a booster will be needed,” Dr Soumya Swaminathan, the World Health Organisation’s chief scientist, said in a Zoom interview on Friday (June 18). The “science is still evolving”.

Such a call is “premature” while high-risk individuals in most of the world have not yet completed a first course of vaccination, Dr Swaminathan said. Data from countries introducing precautionary extra inoculations later this year – particularly for vulnerable people whose immunity to Sars-CoV-2 may wane faster – will inform WHO’s guidance, she said.

Covid-19 booster shots are likely to be rolled out in Britain in autumn to avoid another winter surge. Seven different vaccines are being tested in volunteers in England in the world’s first booster study, Health Secretary Matt Hancock said last month.

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

Tweaking shots

More-transmissible variants, including the Beta strain that emerged in South Africa, require higher antibody levels to prevent infection, prompting vaccine makers, including Pfizer and Moderna, to test whether tweaked versions of their existing shots will provide broader immunity.

One dose of Novavax’s variant-directed vaccine may provide sufficient protection against the Beta strain in individuals previously immunised against Covid-19, according to pre-clinical research released this month by scientists at the Gaithersburg, Maryland-based company and the University of Maryland School of Medicine.

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

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

“Nobody is saying you need a booster today,” Mr Collins said in an interview with biologist Lee Hood at the Precision Medicine World Conference last Thursday.

“But boosters might very well be in our future at some point, and they might be here sooner if other variants pop up”, he added.

As a minimum, vaccines will need to protect against hospitalisation, intensive care unit admission and death, according to Dr Paul Offit, director of the Vaccine Education Centre at the Children’s Hospital of Philadelphia.

“With that bar, we probably would need a vaccine maybe every three to five years,” he said in a Stat biotech podcast last Thursday.

Immunisation with a combination of vaccinations may offer longer immunity or fewer side effects for certain individuals, Dr Offit said.

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Early data from Britain, Spain and Germany suggests a “mix-and-match” regimen using two different types of vaccines generates more pain, fever and other minor side effects compared with two doses of the same inoculation, Dr Swaminathan said.

Still, the so-called heterologous prime-boost combinations appear to spur a more robust immune response, leading to both higher levels of virus-blocking antibodies and the white blood cells that kill virus-infected cells, she said. The concept of mixing vaccines is sometimes called a heterologous prime-boost. 

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

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

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