A 45-year-old nurse in California tested positive for Covid-19 more than a week after receiving Pfizer Inc's coronavirus vaccine, an ABC News affiliate has reported.

Matthew W, a nurse at two different local hospitals, said in a Facebook post on Dec 18 that he had received the Pfizer vaccine, telling the ABC News affiliate that his arm was sore for a day but that he had suffered no other side-effects.

Six days later on Christmas Eve, he became sick after working a shift in the Covid-19 unit, the report added.

Christian Ramers, an infectious disease specialist with Family Health Centres of San Diego, told the ABC News affiliate that this scenario was not unexpected. “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 said.