British health experts are attempting to quash public panic about the Pfizer/BioNTech vaccine which is currently being rolled-out across the UK, following reports that two health workers suffered an "anaphylactoid reaction" just after being immunised.
Such a reaction tends to involve a rash, shortness of breath, swelling of the face and tongue or a drop in blood pressure. UK regulators warned that people with a history of serious allergic reactions shouldn't receive the new vaccine while they investigate the two cases.
Professor Stephen Powis, medical director for the National Health Service in England, said in a statement that the workers are "both are recovering well" and described the regulators' warning as a precautionary measure.
In the meantime, British scientists are calling for calm as public fears of the alleged dangers of the new vaccine — which is said to have an 95 per cent efficacy against infection — threaten to derail the UK's mass inoculation programme.
Dr Penny Ward of King's College London said: "As these two events occurred in people with a history of severe allergy, it is sensible of the MHRA to draw attention to these reports and to suggest that individuals with a history of severe allergy not receive the vaccine at this time."
Professor Graham Ogg of Oxford University urged calm, saying: "It will be important to now understand the specific nature of the reactions and the background medical history of the individuals affected so that any risks of reactions can be more closely defined."
And Professor Peter Openshaw of the Imperial College London said: "As with all food and medications, there is a very small chance of an allergic reaction to any vaccine. However, it is important that we put this risk in perspective."
Allergic reactions to vaccines are usually rare and short-lived. Here's a look at some key questions:
HOW OFTEN DO THEY HAPPEN?
Allergic reactions can occur with numerous vaccines and experts say they are not unexpected. In the Pfizer-BioNTech study of 42,000 people, the rate was about the same in those who got the coronavirus vaccine versus those who got a dummy shot.
US Food and Drug Administration reviewers who examined the study's safety data found that 137 — or 0.63 per cent — of vaccine recipients reported symptoms suggestive of an allergic reaction, compared to 111 — or 0.51 per cent — in the placebo group.
A 2015 study in the US examining the rate of anaphylaxis — a severe, life-threatening allergic reaction — found that it occurred about once per every million vaccine doses.
The study evaluated children and adults who got vaccines against numerous diseases, including polio, measles and meningitis.
"For the general population this does not mean that they would need to be anxious about receiving the vaccination," said Stephen Evans, a vaccines expert at the London School of Hygiene and Tropical Medicine. He noted that even common foods can provoke severe allergic reactions.
WHY DO THESE REACTIONS HAPPEN?
Scientists say people can be sensitive to components in the shot, like gelatin or egg protein, or to the vaccine itself. People with egg allergies are sometimes advised not to get the flu shot, since that vaccine is mostly grown in chicken eggs.
Common symptoms of an allergic reaction include a rash, skin irritation, coughing or trouble breathing.The exact ingredients used in Pfizer's new Covid-19 vaccine are proprietary and are not publicly disclosed. The vaccine uses a new technology, and is coated in lipid nanoparticles, which have been used in drugs.
Some people react to almost any drug or vaccine, said Dr Ashish Jha, dean of Brown University's school of public health. The key is whether reactions to the vaccine are more common or more severe — and that doesn't appear to be the case so far, he said.
WHAT ARE OTHER SIDE EFFECTS?
Typical side effects for many vaccines include things like a sore arm from the shot, fever and muscle aches.
In the Pfizer study, participants also reported fatigue, headache and chills. More serious side effects are reported to regulators or health officials for further investigation. But it can often take time to determine if the vaccine caused the side effect or if the person just coincidentally received the shot before becoming ill.
As for the Covid-19 vaccine, "It's just so high-profile that every little thing that happens all the time is going to get magnified," said Jha.
"We should talk about it, we should be honest with people, but we should put it into context and help people understand," he said. "There is a small proportion of people who have an allergic reaction to almost any medicine."
The UK will continue to vaccinate between 5,000 and 7,000 people per day across the country with 800,000 Pfizer doses already in hospitals and millions more on the way.
- additional reporting Daily Mail