Pfizer has explained that the first jab of its COVID-19 vaccine will offer only 50 percent protection against the disease.
And this will happen in about 10 days.
The pharmaceutical company gave the explanation following the report that a Californian nurse contracted COVID-19, a week after receiving the jab.
Pfizer and a medical expert said the the body needs more time to build up protection.
Pfizer “will review all available information on this case and all reports of any confirmed diagnosis following vaccination,” the drug maker said in a statement to Reuters.
“Based on our Phase 3 safety and efficacy study, the vaccine provides some protection against COVID-19 within about 10 days of the first dose and substantially boosted after the second dose, supporting the need for a 2-dose vaccination series”, it said.
“Individuals may have contracted disease prior to or right after vaccination”, the statement added.
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%, and you need that second dose to get up to 95%.”