An ICU nurse in San Diego, who had received Pfizer vaccine shot against COVID-19 on December 18, has tested positive for the virus.

Matthew W, a 45-year-old nurse in San Diego, told ABC News San Diego affiliate KGTV that after receiving the vaccine he had only experienced arm soreness as a side-effect but six days later after working a shift in the COVID-19 unit, he had chills, muscle pain and fatigue. A coronavirus test confirmed him of being positive.