In a major development, a total of 23 elderly people died within a short time of receiving their first coronavirus vaccine shots in Norway. Apart from the 23, several others have fallen ill soon after the vaccination, triggering Norway to launch a probe into the deaths.

However, a direct connection between the Pfizer vaccine and these deaths is yet to be established, the experts have said 13 of the 23 people who died have shown common symptoms of mRNA vaccines such as diarrhea, nausea and fever.

Allergic reactions have been uncommon so far. In the US, authorities reported 21 cases of severe allergic reactions from Dec 14-23 after administration of about 1.9 million initial doses of the vaccine developed by Pfizer Inc. and BioNTech SE. According to the Centers for Disease Control and Prevention, that's an incidence of 11.1 cases per million doses.

So far, Norway has given at least one dose to about 33,000 people.

Meanwhile, Pfizer has now temporarily reduced its vaccine supply in Europe following the concerns raised with the deaths in Norway.