A San Diego nurse who received the Pfizer vaccine during the initial rollout was diagnosed with a COVID-19 infection on Dec. 26, despite being vaccinated more than a week earlier.
ABC 10 News reports that the nurse, identified Matthew W., works as an Emergency Room attendant in two separate Southern California hospitals, and only noted that after receiving the vaccine, his arm was sore but had no other side effects.
Then, on Christmas Eve, following a shift in a COVID-19 unit, Matthew became ill, with symptoms including chills, muscle aches and fatigue.
On Dec. 26, he tested positive for COVID-19.
While disappointing, this outcome is not unexpected among public health experts, officials say.
“It’s not unexpected at all. If you work through the numbers, this is exactly what we’d expect to happen if someone was exposed,” Christian Ramers, an infectious disease specialist with Family Health Centers of San Diego, told reporters.
Ramers also notes it is possible Matthew was infected prior to receiving the vaccine, and symptom onset occurred after he was vaccinated.
“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,” he added.
At that point, Matthew also only received a single dose of the vaccine. The Pfizer vaccine is composed of two separate vaccines, which are to be given intramuscularly three weeks apart.
Documents issued by the U.S. Centers for Disease Control and Prevention show a single dose of the Pfizer vaccine yields an average 88.9 percent efficacy rate of preventing an infection. Researchers note that a lack of available data for outcomes with participants who only received a single dose of the vaccine “cannot support a conclusion on the efficacy of a single dose of the vaccine” since most participants in clinical trials received both doses.
Ramers says that the efficacy rate after the first dose of the vaccine is likely around the 50 percent mark, and the second dose yields a stronger 95 percent efficacy against the virus.
“You hear health practitioners being very optimistic about it being the beginning of the end, but it’s going to be a slow roll, weeks to months as we roll out the vaccine,” Ramers added.