BioNTech says it hasn't seen any data that would indicate a heightened risk of heart inflammation after Israel announced investigating cases in people who received Pfizer vaccine.
BioNTech has been investigating reports of heart inflammation cases in people who received the Pfizer vaccine in Israel, but so far hasn't seen any data that would indicate a heightened risk, the company said.
"We take everything we hear very seriously," BioNTech's chief executive and co-founder, Ugur Sahin, said on Wednesday.
"The most important principle in drug development is to do no harm."
BioNTech/Pfizer said it has not observed a higher rate of the condition than would normally be expected in the general population.
Some 5 million people in Israel have been vaccinated, primarily with the Pfizer shot, giving it one of the highest coverages in the world.
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Cases of myocarditis in Israel
On Saturday, Israel's Health Ministry said it is examining a small number of cases of heart inflammation in people who had received Pfizer's Covid-19 vaccine, though it has not yet drawn any conclusions.
Israel's pandemic response coordinator, Nachman Ash, said that a preliminary study showed "tens of incidents" of myocarditis occurring among more than 5 million vaccinated people, primarily after the second dose.
Ash said it was unclear whether this was unusually high and whether it was connected to the vaccine.
Most of the cases were reported among people up to age 30.
"The Health Ministry is currently examining whether there is an excess in morbidity (disease rate) and whether it can be attributed to the vaccines," Ash said.
Ash, who spoke about the issue in a radio interview and during a news conference, referred to it as a "question mark," and emphasised that the Health Ministry has yet to draw any conclusions.
Determining a link, he said, would be difficult because myocarditis, a condition that often goes away without complications, can be caused by a variety of viruses and a similar number of cases were reported in previous years.
Pfizer, asked by Reuters news agency about the review, said it is in regular contact with Israel's Health Ministry to review data on its vaccine.
UK and US find no link
The UK's MHRA medicine regulator said there have been no new safety concerns around the Pfizer Covid-19 vaccine and heart inflammation based on the rollout of the shot in Britain.
"The MHRA is as aware of the reports of myocarditis under investigation in Israel. Based on our experience and safety monitoring in the UK, there is currently no new safety concerns raised regarding myocarditis," a MHRA spokeswoman said.
The comment echoed the US Centers for Disease Control and Prevention (CDC) which said it had not seen a link between the shot and heart inflammation.
CDC director Rochelle Walensky said the US had not seen a link between heart inflammation and Covid-19 vaccines on Tuesday.
"We have not seen a signal and we've actually looked intentionally for the signal in the over 200 million doses we've given," Walensky said in a press briefing.
She said the CDC is in touch with the US Department of Defence over its investigation of 14 cases of heart inflammation or myocarditis among people who were vaccinated through the military's health services.