Fully vaccinated persons are 11 times less likely to die from Covid-19 and 10 times less likely to be hospitalised now that the Delta variant has become the main strain of the virus in the United States, health authorities there announced on Friday.
"Looking at cases over the past two months when the Delta variant was the predominant variant circulating in this country, those who were unvaccinated were about four and a half times more likely to get COVID-19, over 10 times more likely to be hospitalized, and 11 times more likely to die from the disease," CDC Director Rochelle Walensky said at a briefing on Friday. Study after study has shown that vaccination works, she stressed.
The figures were published in three articles in the Morbidity and Mortality Weekly Report, which is produced by the CDC, the main federal public health agency in the United States. They confirm the continued effectiveness of anti-COVID vaccines against the most severe strains of the virus.
The CDC’s announcement came one day after U.S. President Joe Biden unveiled his government’s new strategy to overcome COVID-19, which includes a decree mandating employees of companies with over 100 workers to be vaccinated or undergo weekly tests.
The first study analysed hundreds of thousands of COVID-19 cases in 13 U.S. locations for the period from 4 April to 19 June this year, before the spread of the Delta variant, then compared them with cases of infection from 20 June to 17 July.
Between the two periods, the likelihood of a fully vaccinated person being infected with COVID-19 compared to an unvaccinated person did, however, increase, going from 11.1 times less likely to 4.5 times less likely.
The protection offered by the vaccine against hospitalisation remained stable, but it decreased more among people aged 65 years and over than among people in the younger age groups.
U.S. health authorities are currently assessing the need for booster shots. Senior citizens will probably be the first to receive them when the U.S. Government announces the next vaccination campaign on 20 September.
Another of the studies evaluated the effectiveness of the various vaccines between June and August in over 400 hospitals and health centres. It found that Moderna was more effective against hospitalisation (95%) than Pfizer (80%) and Johnson & Johnson (60%).
It was not fully clear why Moderna seemed to provide higher protection against the Delta variant than Pfizer. However, this could be related to a higher dosage (100 microgrammes versus 30 microgrammes) and the longer interval between first and second dose (four weeks for Moderna, three for Pfizer), which lead to a stronger immune response.
The Brussels Times