From the WebMD Archives

April 2, 2021 -- The Pfizer/BioNTech COVID-19 vaccine affords at least 6 months of protection following the second dose, the companies announced today.

The vaccine was 91.3% effective against COVID-19 in an analysis of 927 symptomatic people through March 13, as indicated by real-world data compiled since the vaccine was given emergency use authorization. This compares to 95% efficacy reported in the interim results that were announced on Nov. 18, 2020.

Data released today also show the vaccine affords 100% protection against severe COVID-19, as defined by the CDC.

The vaccine was likewise effective in preventing COVID-19 in South Africa, where the variant of concern B.1.351 was first identified.

‘Very Encouraging’ Finding

"Real-world data are often different than what was found in clinical trials. That is because the people enrolling in clinical trials have to meet certain inclusion and exclusion criteria," John Segreti, MD, told Medscape.

"Often the real-world results are worse than the trial results. This finding is therefore very encouraging," said Segreti, hospital epidemiologist, medical director of infection control and prevention, and professor of internal medicine at Rush Medical College inChicago.

"The finding that efficacy lasts at least 6 months is not surprising," he added, but it is "very encouraging."

William Schaffner, MD, agreed that this is "very good news." The 6-month duration of protection and the vaccine's efficacy against the South African variant make "the light at the end of the tunnel a little bit brighter.

"We're delighted that we can now say rather firmly that it will last at least 6 months. That's how much we can measure securely at the present time, and the clock is still running," Schaffner said. He is professor of medicine in the Division of Infectious Diseases, at Vanderbilt University Medical Center in Nashville. The trial is ongoing,

Protection Against Major Variant

The South African variant "has been the most concerning variant so far," Segreti said. "While current vaccines may be less effective in preventing infection with this variant, the finding that the vaccine is effective in decreasing hospitalizations and death is very important news," he said. He noted that it should convince more people to get vaccinated.

Schaffner said he was "a little more cautious" but that "it's great that it offers protection against the South African variant." He said that repeated infections have been reported in that country, "so that's the one we're most worried about.

"If Pfizer's antibodies really do provide some protection ― maybe even a lot of protection ― against this strain, that would be a terrific bonus," he said.

Schaffner pointed out that it is unknown whether the same success can be found with the Moderna or Johnson & Johnson vaccines. "We can feel a degree of comfort that at least the Pfizer product does also protect against the South African strain, and we're really quite sure it will protect against the British strain ― that would reduce the need for us to have a booster program right away."