Can Pfizer’s corona vaccine affect people’s health? Is it harmful ??

Pfizer’s corona vaccine has been introduced in Britain. But only 24 hours after the vaccination, the health of 2 health workers deteriorated. According to the health service there, the health has deteriorated due to the vaccine, which has also increased the concern of the government there.
We all know that Pfizer has also sought approval for its vaccine in India. But because of this case, India once again wondered whether it would be right. Wouldn’t people be harmed by this vaccine?

Currently the British government refuses to vaccinate people who are allergic to the vaccine.