Pfizer and BioNTech’s coronavirus vaccine inched a step closer toward approval on Monday, with the company announcing 90% efficacy in phase 3 clinical trial. The vaccine will be offered in a two-dose jab, not unlike other candidates currently in development and a multitude of multi-dose medicines that have come before it.
The vaccine’s two doses will be separated by a period of 21 days, with the first shot occurring on day zero, Dr. Anuj Mehta, a pulmonary and critical care physician at National Jewish Health, explained to Fox News. The period between the two shots is based on data collected in the lab before the vaccine was tested in humans, he explained.
Each dose will be comprised of the same formulation, meaning there is no difference between the shots, but the reason there has to be two is because the body responds to each differently. The first dose, Mehta said, acts as a primer for the body’s immune system, and the second dose, given three weeks later, will kick it into gear, so to speak.
Mehta, a member of the medical advisory group of the Governor’s Expert Emergency Epidemic Response Committee in Colorado who is not involved in Pfizer’s trials, said after the second dose the body will be able to better recognize the proteins created by the COVID-19 virus, translating into immunity.
How long that immunity lasts, however, remains to be seen.
“Based on the press release from Pfizer, it appears that the immunity sets in within a week of the second dose,” Mehta said, citing the press release published by Pfizer. “All the data supports the fact that a single-dose won’t provide really robust immunity, which is what we need to combat the pandemic.”
Mehta added that it’s too soon to know if the vaccine will be an annual inoculation, similar to the flu shot, or if it will be effective for several years.
“We don’t know if this is going to be something where people need repeated immunizations at different time intervals, or it’ll be sufficient for a very long period of time,” he said. “Long-term follow up included with the trials will tell us that.