Companies provide update on durability of shot’s immune response based on continuing analysis of late-stage trial
By Jared S. Hopkins – The Wall Street Journal.
The Covid-19 vaccine from Pfizer Inc. PFE 0.19% and BioNTech SE BNTX 4.29% remains highly effective six months after its second dose, an indication that protection could last for an even longer period.
The findings, released on Thursday, emerged from a continuing review of how volunteers in the shot’s late-stage trial were faring and whether they contracted Covid-19 with symptoms.
In the rush to introduce vaccines for a new virus, companies and other vaccine researchers were unable to determine how long shots would provide protection, or whether booster shots would be needed to ensure protection.
Pfizer said it hopes to provide more information on protection beyond six months in the coming weeks. The companies said they planned to continue to monitor study subjects for two years. Some vaccines, such as the one for measles, provide lifelong immunity while others, such as for the flu, need to be given every year.
The further analysis suggested the vaccine worked effectively against a variant first identified in South Africa, Pfizer and BioNTech said. And the companies said they haven’t found serious safety concerns so far.
“It is an important step to further confirm the strong efficacy and good safety data we have seen so far, especially in a longer-term follow-up,” said BioNTech Chief Executive Ugur Sahin.
Pfizer Chief Executive Albert Bourla said the additional results provide “further confidence in our vaccine’s overall effectiveness.”
The companies said they now expect to file for full approval of the vaccine in the U.S. as early as this month. It has been cleared for use so far on an emergency basis.
The vaccine was the first authorized in the West last year, after the late-stage, or Phase 3, trial found it was 95% effective at preventing Covid-19 with symptoms and was generally safe.
In the U.S., the vaccine is cleared for use in people age 16 and older.
The shot has now become a key cog in global vaccination efforts. The companies have distributed more than 200 million doses globally and plan to produce 2.5 billion doses this year.
On Wednesday, the companies said the vaccine was 100% effective in children ages 12 to 15, results that could lead to the vaccine’s U.S. authorization for use in adolescents in May.
The vaccine uses a new gene-based technology, named messenger RNA after the molecules that carry genetic instructions to cells to make proteins. Production of the proteins trains the immune system to recognize the coronavirus and fight it.
The new analysis looked at the vaccine’s performance in 46,307 people who enrolled in the Phase 3 trial, starting in July.
Of the 927 cases of symptomatic Covid-19 observed through March 13, 850 were in people who received a placebo and 77 in people who were vaccinated, according to the companies.
That corresponds to a vaccine efficacy of 91.3% up to six months after getting the second dose, Pfizer and BioNTech said.
The protection remained generally consistent across age, gender, race and ethnicity, as well as among individuals with underlying health conditions, the companies said.
The vaccine was also 95% to 100% effective against severe disease, with the precise figure depending on whether researchers used a definition of severe disease from the U.S. Centers for Disease Control and Prevention or one from the U.S. Food and Drug Administration.
Some 800 trial subjects were enrolled in South Africa, where a more contagious variant of the virus was first identified. Among those volunteers, there were nine cases of Covid-19, all in people who got a placebo. Sequencing confirmed six of the nine cases were of the variant.
The findings, the companies said, support earlier analyses that have shown the vaccine generated a slightly lower immune response against the variant than the more common strain circulating in the U.S., but was still effective at neutralizing the variant virus.
Of the 697 cases of symptomatic Covid-19 among study subjects in the U.S., 647 were in people who received a placebo, with the rest in vaccinated subjects, indicating 92.6% efficacy, according to the companies.
Despite the success of Covid-19 vaccines, health authorities and vaccine experts have said it is possible that booster shots will be needed seasonally or annually to ensure protection until the virus is fully stamped out around the world. They also say the vaccines might need to be updated to address potential variants that escape protection.
Pfizer and BioNTech last month began testing people to determine whether the companies’ Covid-19 shot can provide protection against emerging strains of the coronavirus, such as the one first identified in South Africa. They are also in discussions with regulators about studying a tweaked version of their vaccine that researchers designed to protect against the variant found in South Africa.
Pfizer has previously said it anticipates producing the Covid-19 shots for at least several years on the expectation that booster shots will be needed annually or every few years to maintain protection.
Featured article licensed from the Wall Street Journal.