People with allergies are being urged to come forward and get their booster jabs after concerns about anaphylactic reactions had "no scientific basis".
Many are reporting being turned away from vaccination centres because they tell staff they have a history of anaphylaxis to food, venom, or to an identified medicine.
Health workers are often wrongly informed they need give people with allergies an AstraZeneca vaccine as a booster, allergy charities say.
Allergy UK and The Anaphylaxis Campaign say they are facing a deluge of desperate enquiries in response to the government’s promotion of the importance and urgency of the booster vaccination.
Previous information has led people living with allergies to believe that the preferred Pfizer booster will put them at risk of anaphylaxis.
The two charities, as well as the British Society for Allergy & Clinical Immunology (BSACI), are now calling for urgent action to share latest Green Book vaccination guidance.
The Green Book has the latest information on vaccines and vaccination procedures, for vaccine preventable infectious diseases in the UK.
The charities say the Green Book should reassure the majority of the allergic population, who largely received AstraZeneca for first and second doses, that they can safely receive the Pfizer vaccination as a booster.
An Allergy UK spokeswoman said: "Initial concerns for people with allergies were alleviated three weeks after being raised, when guidance by the MHRA was reversed.
"Two healthcare workers had been reported to have suffered anaphylactic reactions to their Pfizer vaccines in the first week of the COVID-19 vaccine roll-out in December 2020.
"But, on investigation, there was no scientific basis for concern for the large majority of individuals with food, venom (bees and wasps) or known medicine allergies, even if they had experienced anaphylaxis before."
She added: "Unfortunately, the message that Pfizer was not suitable for people with allergies, and in particular for people with any history of anaphylaxis, spread far and wide.
"It has proved extremely difficult to correct this message.
"When the Oxford AstraZeneca vaccine was authorised, people with any allergy whatsoever were frequently told that AstraZeneca was more suitable and safer for them.
"So they received their two doses of that vaccine instead.
"This was despite the guidance by that time being very clear that there was NO REASON for them to fear the Pfizer vaccine."
The AstraZeneca vaccine is also difficult to arrange as a booster and is not usually offered in booster clinics.
As a result, the charities report that patients often end up running round in circles between their GP and 119 operators, who frequently are unable to offer any guidance.
The ingredient in the Pfizer vaccine that originally caused concern is called polyethylene glycol (PEG for short, and also known as Macrogol) and is a common ingredient in medicines.
Most allergic reactions caused by PEG have resulted from laxatives and some types of steroid injections, but it is an extremely rare cause of anaphylactic reactions and only individuals with a history of anaphylaxis immediately after taking medicines containing PEG need to seek further specialist allergy advice before vaccination.
As the vaccine roll-out has continued, studies have shown that even people known or suspected to have an allergy to PEG can be safely vaccinated with the Pfizer vaccine.
There has been just one case report in the medical literature of anaphylaxis with the Pfizer vaccine caused by PEG.
Allergy UK says: "You CAN have a Pfizer or Moderna booster if:
- you have any type of FOOD allergy (including anaphylaxis)
- you have had anaphylaxis to WASP or BEE stings
- you have an identified allergy to most medicines
- any current or recent medications that you have taken safely contain Polyethylene glycol (PEG/Macrogol)"
The charity added: "You do need to seek further allergy advice if you have had immediate anaphylaxis to multiple unrelated medicines that contain Polyethylene glycol (PEG/Macrogol). You can check ingredients of medicines at medicines.org.uk if you are not sure."
