New York, Dec 30 (IANS): A nurse in California tested positive for Covid-19 eight days after receiving the first dose of the Pfizer vaccine approved for emergency use in the US.

Matthew W., 45, talked about receiving the vaccine on December 18 in a Facebook post, said the report on Tuesday.

He told ABC 10News that he suffered no other side effects other than that his arm was sore for a day.

However, he became sick on Christmas eve after working a shift in the Covid-19 unit.

Matthew got himself tested the day after Christmas and the results showed that he was Covid-19 positive.

Christian Ramers, an infectious disease specialist with Family Health Centers of San Diego told the ABC News affiliate that testing positive after the first dose is not unexpected if someone is exposed to the virus.

"We know from the vaccine clinical trials that it's going to take about 10 to 14 days for you to start to develop protection from the vaccine," Ramers was quoted as saying.

The Phase 3 data from Pfizer demonstrated a vaccine efficacy rate of 95 per cent in participants without prior SARS-CoV-2 infection and also in participants with and without prior SARS-CoV-2 infection, in each case measured from seven days after the second dose.

The vaccination regime submitted by Pfizer-BioNTech requires two doses of vaccine to be administered 21 days apart.