PHOENIX (3TV/CBS 5) -- A COVID-19 vaccine may protect you from getting sick, but it is unclear whether it might prevent the spread of the virus. Pfizer released a report on its vaccine ahead of its FDA review Thursday. The Pfizer vaccine may soon be approved for emergency use and distributed throughout the Valley.

Pfizer reports its vaccine is 95-percent effective at preventing COVID-19. Pfizer also reports the two-shot vaccine is effective even after the first dose. According to the FDA briefing document, the Pfizer vaccine is 52-percent effective at preventing COVID-19 after the first dose and 89-percent effective at preventing severe illness.

“What we don’t know from these studies is what their impact is on the rate of asymptomatic but still contagious Covid,” says Dr. Melanie Swift, occupational medicine physician at Mayo Clinic. “So we can’t rip off our masks just yet because we had our vaccines.”

Mayo physicians say it will be important to continue following public health guidelines until transmission goes down.

Dr. Abinash Virk, an infectious disease physician at Mayo Clinic, says the vaccine might keep you from getting sick or severely sick, but it’s unclear if it can prevent you from unknowingly shedding the virus and infecting someone else.

“Whether you pick up the virus and don’t have any symptoms and give it to somebody else, that part we don’t know,” says Virk. “But we know you won't get sick from it and you certainly won’t get severe Covid which is obviously the biggest concern."

Mayo physicians say the Pfizer document shows potential side effects are mild and that older participants experienced fewer side effects. Nearly 44,000 participants were part of the clinical trial which included people as young as 16 years old.

The Pfizer document acknowledged more data is needed to assess the effect of the vaccine in preventing transmission. The report warns "asymptomatic cases in combination with reduced mask-wearing and social distancing could result in significant continued transmission".


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