Segun Akanni, Toronto, Canada 
A medical expert explained the body needs more time to build up immunity.
Matthew W., 45, a nurse at two different local hospitals, said in a Facebook post on December 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. He got the chills and later came down with muscle aches and fatigue.
He went to a drive-up hospital testing site and tested positive for COVID-19 the day after Christmas, the report said.
Christian Ramers, an infectious disease specialist with Family Health Centers 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.
“That first dose, we think, gives you somewhere around 50 percent, and you need that second dose to get up to 95 percent,” Ramers added
