Q: How long will protection last following vaccination?
A. We do not know how long protection will last following vaccination but it will be critically important to measure long-term protection in the phase 3 trials and in other groups prioritized for early vaccination. We are still learning about the duration of protection following infection with COVID-19 and it is too early to tell how long protection will last.
Q. Can a vaccinated person still transmit the SARS-COV-2 virus that causes the COVID-19 disease?
A. Additional studies have shown that Pfizer-BioNTech and Moderna vaccines not only prevent people who are exposed to the virus from contracting COVID-19, but also prevent them from spreading the virus to others.
More data is currently being collected to provide definitive answers regarding infectiousness and transmissibility of COVID-19 by those who have been vaccinated. However, large studies have demonstrated that vaccinated persons have significantly fewer coronavirus infections, both asymptomatic (89.4%) and symptomatic (93.7%) based on nasal swab PCR tests, than found among unvaccinated persons.
The Centers for Disease Control and Prevention (CDC) recommends continuing to practice public health protective measures like washing your hands, wearing a mask, physical distancing, and frequently cleaning common areas.
Q: Can I still get sick with the COVID-19 disease once I have been vaccinated?
A: Yes, even though the vaccine is highly effective (has a high efficacy), it’s still possible for a vaccinated person to become ill. The protection provided by the vaccine is not immediate after receiving the second dose. Current information indicates it takes time for a person’s immune system to fully respond to the vaccine and produce antibodies. According to the Centers for Disease Control and Prevention (CDC), evidence from clinical trials indicates that the Pfizer vaccine reaches full potential, 95% efficacy, at least 7 days after the second dose. At the 95% effective rate, approximately 5% of those who receive both doses of the vaccine may still get the COVID-19 disease. Clinical trial data for the Moderna vaccine indicate that it reaches full potential, approximately 94% efficacy, at least 14 days after the second dose.
You can read more from the CDC about the different COVID-19 vaccines, including Pfizer and Moderna, at https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines.html.