The British government has now scrapped mandatory self-isolation rules, with the Prime Minister Boris Johnson stating that vaccines will remain the first line of defence against the Covid-19 virus.
Further boosters will be offered this spring for the most vulnerable, while children over 12 are currently being offered their second doses.
All children aged five to 11 in the UK will be offered a low dose of a covid vaccine later this year.
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As with all vaccines, covid jabs and boosters may have some side effects.
The Government's list of common side effects includes pain and swelling at the injection site, tiredness and a fever.
However, recent data from the ZOE covid app said people have reported an unusual after-effect, and that it appears in the mouth.
Professor Tim Spector, who helped found the Zoe study, explained during a Youtube video.
Prof Spector said: "[There is] a side effect of vaccines ... this concerns a metallic taste in the mouth."
He also said people have reported bleeding at the site of vaccines.
Prof Spector continued: "There have been various reports of metallic taste, or bleeding at the site of vaccines for many years, even before covid, as a general phenomenon of people having all types of injections into muscles."
He said around 3.6% of people who reported having had vaccinations said they had experienced a metallic taste in the mouth, while 0.9% had bleeding at the injection site.
The professor clarified that he had "no evidence that either side effect is of any concern at all".
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