The stocks of BioNTech, Pfizer and Moderna, which make the COVID-19 mRNA vaccine, fell amid news the jabs could be linked to rare heart inflammation in young people.
A Centers for Disease Control and Prevention (CDC) advisory panel said there is a “likely association” between adolescents getting the vaccines and cases of myocarditis and pericarditis, but it added that the benefits are still greater than the risks.
US futures are trading higher, indicating positive investor sentiment after Federal Reserve chair Jerome Powell reiterated a dovish monetary policy stance, said Naeem Aslam, chief market analyst at Ava Trade.
Meanwhile, BioNTech (BNTX) was down almost 3% when markets closed in the US, and gained 0.5% pre-market.
The CDC is monitoring cases reported after first and second doses of the Moderna and BioNTech/Pfizer mRNA vaccines in people aged over 12.
There were 323 confirmed cases among people who received the vaccine of either myocarditis and pericarditis, or both, in the US up to June 11, the FT reported. Almost 80% have fully recovered.
The side-effects were most common in men aged 30 years and younger.
In those aged 12 to 39 there were 4.4 reports per million vaccine doses administered of either type of inflammation. The rate rose to 12.6 per million after the second dose.
The CDC is recommending delaying second doses if an adolescent experiences the rare condition after the first shot.
Studies found some people who got the jabs suffered from rare blood clots. The rollout of both was paused in many countries earlier this year.
Meanwhile, a study by Imperial College of over half a million adults in England found that one in 20 had persistent COVID-19 symptoms. This could mean that more than 2m people in England may have been affected by these persistent symptoms.
More than 43 million people in the UK have received at least one dose of a coronavirus vaccine.
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