US considers booster shots amid concerns of J&J vaccine’s effectiveness against Delta variant

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Health officials in the United States are weighing the need for booster shots for Americans who received the Johnson and Johnson COVID-19 vaccine amid growing concerns around how protective the single-dose is against the more contagious Delta variant.

The US Centres for Disease Control has warned that the variant – first identified in India – could become the dominant strain in the United States.

The variant is also driving a massive resurgence of infections in South Africa as the country moved back to alert Level 4, just one level below full lockdown.

Available data does confirm the efficacy of the mRNA vaccines against the variant – either Pfizer-BioNTech or Moderna – but the science is less clear about the single J&J dose against Delta, which is highly transmissible and associated with more severe disease.

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The Director of the Centres for Disease Control, Dr Rochelle Walensky, says they are closely monitoring the prevalence of the Delta variant in the US.

“In the last two weeks, the prevalence of cases resulting from the Delta variant has doubled to just over 20%, as Dr (Anthony) Fauci just showed. This variant represents nearly half of all infections in HHS Regions 7 and 8. This is concerning but expected, knowing what we do about how efficiently this variant spreads and by what we saw in the United Kingdom with this variant. We know our vaccines work against this variant. However, this variant represents a set of mutations that could lead to future mutations that evade our vaccine. And that’s why it’s more important than ever to get vaccinated now, to stop the chain of infection, the chain of mutations that could lead to a more dangerous variant,” says Walensky.

Experts are now weighing the option of following the single J&J shot with a second mRNA dose in order to produce a stronger immune response against the Delta variant.

While studies in the UK show that two doses of either Pfizer-BioNtech or AstraZeneca are significantly more protective against the variant than the single J&J dose.

Director of the US National Institute of Allergy and Infectious Diseases, Dr Anthony Fauci, says Pfizer-BioNTech and Oxford-AstraZeneca are 92 to 96% effective against hospitalisations.

“Here is now some of the good news and one of our tools. The effectiveness of the vaccines – in this case, two weeks after the second dose of Pfizer-BioNTech – was 88% effective against the Delta and 93% effective against the Alpha when you’re dealing with symptomatic disease. When you look at hospitalizations, again, both the Pfizer-BioNTech and the Oxford-AstraZeneca are between 92 and 96 percent effective against hospitalizations. You put all of these things together, and you come to what we would call a “self-evident conclusion. Similar to the situation in the UK, the Delta variant is currently the greatest threat in the US to our attempt to eliminate COVID-19. Good news: Our vaccines are effective against the Delta variant,” he says.

Johnson and Johnson says it’s testing whether the immune response from its vaccine is capable of neutralising the Delta variant in a laboratory setting, but no data is available yet.

Health experts emphasise the importance of getting vaccinated in order to reduce the likelihood of new COVID-19 mutations that could pose additional challenges to the efficacy of the existing vaccines.