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Pfizer Coronavirus Vaccine Provides Significant Immunity After One Dose, Doesn't Need Ultracold Temperatures, New Research Finds

CLEVELAND, Ohio — The Pfizer COVID-19 vaccine provides significant immunity after one dose, and can be stored in ordinary freezers instead of at ultracold temperatures, according to new research and data released by Pfizer.

The new research and data regarding the efficacy of one shot of the Pfizer vaccine, along with higher storage temperatures, could greatly simplify the logistics of the vaccine rollout in the United States and enable more people to get immunized.

The new research regarding the efficacy of one dose, based on an Israeli study and published in the Lancet, was based on an evaluation of about 9,000 people in Israel.

Pfizer's clinical trials initially showed that its vaccine prevented roughly 52% of infections after one dose, and close to 95% of infections after two doses.

The Israeli study found that the first shot of Pfizer's vaccine actually prevented about 75% of infections, and 85% of symptomatic infections, up to 28 days after it was administered.

The findings about one-dose efficacy, published in the Lancet, echo a letter written by two Canadian researchers and published in the New England Journal of Medicine this week.

The second dose of Pfizer's COVID-19 vaccine could be delayed in order to stretch supplies, two Canada-based researchers said in a letter published in the New England Journal of Medicine. The first shot protects nearly as well as two shots against cases of severe COVID-19, the letter said.

The United Kingdom is already taking this approach as a way to give more people initial protection against the coronavirus.

One-dose research

There were limits to the Israeli study.

It measured the efficacy of the first vaccine dose 15 to 28 days after it was given. That's not very different from Pfizer's recommendation that patients receive the second dose 21 days after the first shot. Most participants in the Israeli study did get their second shots, according to press reports.

Researchers also don't know how long protection from the first dose will last.

Health experts in France are debating whether to give people who have recovered from COVID-19 only one vaccine dose instead of two, in order to free up doses for others.

The World Health Organization said in January that under "exceptional circumstances," the second dose of the Pfizer vaccine can be given up to six weeks after the first.

In their letter, Canadian researchers Danuta Skowronski and Gaston De Serres analyzed data submitted by Pfizer to the Food and Drug Administration, and determined that the first dose of the vaccine has an approximately 92.6 percent efficacy rate.

Pfizer's response to the researchers' letter, also published in The New England Journal of Medicine, stated that "alternative dosing regimens" for its vaccine have not yet been properly evaluated.

"The decision to implement alternative dosing regimens resides with health authorities," Pfizer continued. "However, we at Pfizer believe that it is critical for health authorities to conduct surveillance on implemented alternative dosing schedules to ensure that vaccines provide the maximum possible protection."

New temps for storage

Pfizer's new data shows that its vaccine can be stored safely at -25 C to -15 C (-13 F to 5 F), temperatures more commonly found in pharmaceutical freezers and refrigerators.

Previously, the pharmaceutical company said the vaccine required storage at ultracold freezers at temperatures between -80 and -60 degrees C (-112 F to -76F).

Pfizer has submitted new data to the U.S. Food and Drug Administration to seek a proposed update that would allow for vaccine vials to be stored at these temperatures for a total of two weeks as an alternative or complement to storage in an ultralow temperature freezer.

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COVID Vaccine Effectiveness After First Dose And How Long It Takes To Build Immunity

How effective is a single dose of the COVID-19 vaccines that are currently available in the United States? And how long does it take to build up maximum immunity after receiving the shots?

Both the Pfizer-BioNTech and Moderna vaccines appear to provide some protection after the first dose. But their headline efficacy ratings are only based on assessments of people who have received two shots.

Pfizer-BioNTech

Clinical trials evaluating the Pfizer-BioNTech vaccine, which requires two shots given 21 days apart, reported an efficacy of 52 percent after the first dose.

In a large-scale Phase III trial, participants were given either two full doses with a 21-day interval or a placebo.

A study published in the New England Journal of Medicine detailing the results reported 39 cases of COVID-19 in the vaccine group and 82 in the placebo group, suggesting an efficacy of 52 percent between the first and second dose.

The vaccine only provides maximum protection "seven or more" days after the second dose is administered.

Clinical trials have shown that after this second dose, the Pfizer-BioNtech vaccine reduces an individual's risk of developing COVID-19 by around 95 percent.

In addition, trial data indicates that the first dose only begins to provide some form of protection after around 12 days.

Other experts have provided different estimates for the vaccine's efficacy after the first dose but these figures have been calculated in different ways to the one provided by the clinical trial researchers.

For example, the U.K.'s Joint Committee on Vaccination and Immunisation (JCVI) calculated that the Pfizer-BioNtech vaccine's short-term efficacy was 89 percent between days 15 and 21 after the first dose.

This calculation did not take into account the time period when the first dose hadn't begun to work, unlike the figure provided in the clinical trials.

But Sheila Bird, a biostatistician from Cambridge University, said in a statement that while there appears to be "some protection against COVID-19 disease following one dose," the available data does not "provide sufficient information about longer-term protection beyond 28 days after a single dose."

The graphic below, provided by Statista, shows the countries with the highest rate of COVID-19 vaccination.

Statista

In addition, a paper posted to the pre-print server medRxiv on January reviewing real-world data from Israel's world-leading vaccine rollout has provided more data on the Pfizer shot's efficacy after one dose—although the study has yet to be peer-reviewed so its findings should be viewed with caution.

The researchers concluded that the vaccine was 51 percent effective against SARS-CoV-2 infection 13-24 days after immunization with the first dose.

But Ben Poole, a research scientist at Google Brain, reanalyzed the data provided in the study, suggesting that protection was actually significantly higher after the first dose.

"One dose of the mRNA COVID-19 vaccine may reduce infections by greater than 75 percent, not just 50 percent," Poole tweeted. "The study averages effectiveness over days 13-24, but reanalyzing the data shows greater effectiveness after 20 days. Great news for vaccines!"

Moderna

The Moderna vaccine, which requires two doses spaced 28 days apart, has an efficacy of 94.5 percent against COVID-19 at least 14 days after the second dose was given, clinical trials have shown.

Unlike Pfizer-BioNTech, Moderna actually conducted an additional analysis in their clinical trials among a subset of participants to assess the efficacy of their vaccine after only one dose.

According to a U.S. Food and Drug Administration (FDA) document, reviewing the clinical trial data, vaccine efficacy after one dose was around 80 percent, with a median follow-up time of 28 days.

But the FDA said the small, non-random sample and short median follow-up time "limits the interpretation of these results."

"There appears to be some protection against COVID-19 disease following one dose; however, these data do not provide sufficient information about longer term protection beyond 28 days after a single dose," the FDA document says.

A similar analysis was conducted to look at the vaccine's efficacy against severe COVID-19 after one dose, which appears to be around 90 percent. But again, these findings should be interpreted cautiously due the small sample size and short follow-up duration.

A health worker prepares a dose of the Pfizer-BioNtech COVID-19 vaccine at Clalit Health Services, in a gymnasium in the Israeli city of Petah Tikva, on February 1, 2021. A health worker prepares a dose of the Pfizer-BioNtech COVID-19 vaccine at Clalit Health Services, in a gymnasium in the Israeli city of Petah Tikva, on February 1, 2021. JACK GUEZ/AFP via Getty Images

Pfizer Says A 3rd Dose Of Its COVID-19 Vaccine Boosts Immunity

Pfizer presented data to investors showing that a third dose of its COVID-19 vaccine boosts immunity. The company believes everyone will need a boost eight to 12 months after receiving a second shot.

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