When the Pfizer vaccine was first approved it was recommended that you should only avoid having it if you’d already reacted either to the vaccine itself or a constituent component of it. The Pfizer coronavirus vaccine (and the Moderna one) contains a substance called Polyethylene glycol (PEG), which a very small number of people are allergic to. Therefore, if you know there is an issue with PEG, it’s very important to avoid these vaccines and go for the Oxford/ AstraZeneca one which does not contain PEG (but has similar contra indications regarding avoiding it if you’re allergic to any of the vaccine components).
It is still not completely clear what caused the allergic reactions that have been reported in the media. From the extensive experience in using the Pfizer vaccine in the UK over the last few weeks, with over a million doses given, it looks like allergic reactions effect less than 1 in 100,000 people and there has not been anything to suggest that having food allergies is a particular risk. Whilst there was a brief period when the MHRA in the UK issued cautious advice suggesting that those with a history of anaphylaxis to anything (whether it was a vaccine, drug or food), avoid the Pfizer vaccine, this advice has now been changed back to the original advice and there is no need for food allergic patients, even if they have had anaphylaxis in the past, to avoid the vaccination.
None of the Covid vaccines are approved for use for children as it stands and they are unlikely to be offered them in the near future.