Tuesday, 9 August, 2022
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WHO: Omicron more transmissible but not necessarily milder

The Omicron variant, already detected in nearly 60 countries, may be more transmissible, but increased transmissibility does not necessarily mean it will cause less severe disease, says the World Health Organization (WHO).

While its global spread and large number of mutations are causing concern, reports MedPage Today, WHO said it was too early, however, to draw conclusions, given the lack of data on clinical disease.

Dr Mike Ryan, executive director of WHO's health emergencies programme, said although a virus will adapt to become more transmissible, the idea that a more transmissible virus is a milder virus is “a little bit of an urban legend”.

“The outcome of whether a virus is less severe is much more random,” he said. “I don’t expect in general for viruses to become milder, it can happen randomly, but it’s not a process that as a disease becomes more transmissible, it becomes milder.”

If mild disease goes unchecked, it can generate pressure on the healthcare system, he added.

“Hope is not a strategy and we need to be very, very careful” when talking about severity, he said.

However, COVID-19 boosters for all are not the answer either, said Dr Kate O’Brien, the WHO’s director of the Department of Immunization, Vaccines and Biologicals, adding that the organisation’s Strategic Advisory Group of Experts on Immunization (SAGE) recently met for an “intensive review” on boosters. Preliminary data showed the vaccines were “holding up” for the severe end of the disease spectrum, while there had been “further reductions in performance” on the mild end.

“However you look at it, primary doses always outperform booster doses for those who are at risk,” she said. “Primary doses to those who have not been vaccinated have to be the priority.”

Dr Soumya Swaminathan, the WHO’s chief scientist, added that boosters make sense for vulnerable populations, for those with comorbidities, but “are unfortunately not the solution to this”.

WHO officials referenced several early reports on lab data showing a reduction in neutralising antibodies for the Pfizer vaccine, but pointed out that neutralising antibodies are only one component of immunity. More clinical data are needed, they said, especially in countries with different populations, such as South Africa, which has a younger population. They also noted early reports on increased risk of reinfection with Omicron, but stressed these were also preliminary.

O’Brien said that while vaccine performance might be affected by the variant, that did not mean vaccines would become “ineffective entirely”. She added that herd immunity is more important than ever, noting that people “can’t rely on the concept that other people being vaccinated will protect those in the community who choose not to be vaccinated”.

By that same token, Ryan said that while preliminary indications are that Omicron is transmitting more efficiently than Delta, that “does not mean the virus is unstoppable”, rather that it has become “better adapted to exploiting the connections between us”.

That means non-pharmaceutical interventions, such as masking and social distancing, are particularly important, WHO officials said.


MedPage Today article – WHO: Omicron More Transmissible, Not Necessarily Milder (Open access)


See more from MedicalBrief archives:


Triple shot of Pfizer vaccination ‘neutralises Omicron variant’


So far, milder disease seen with Omicron, with shorter hospital stays — SA hospitals analysis


Omicron: Some simple steps to deal with the new variant


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