Pfizer reported Wednesday that the power of its two-dose Covid vaccine wears off slightly over time, but it still offers lasting and robust protection against serious illness. The company suggested that a third vaccination could improve immunity, but whether boosters are needed on a large scale is far from clear and is a hot topic of debate among scientists.
So far, federal health officials have said boosters are unnecessary for the general population. And experts wondered if vaccinated people should get more doses when so many people are vaccinated at all.
“Right now, there isn’t enough evidence that this is somehow the best use of resources,” said Natalie Dean, biostatistician at Emory University in Atlanta.
Still, the results raise the question of how far the Pfizer vaccine will prevent infection in the coming months. And as coronavirus cases rise again in many states, the data may affect the Biden government’s deliberations about delivering boosters to the elderly.
If the third shot were released to the general population, the boosters would likely be a billion dollar business for Pfizer.
In a study published online but not yet peer-reviewed or published in a scientific journal, Pfizer and BioNTech scientists reported that the vaccine had a sky-high rate of effectiveness of about 96 percent against symptomatic Covid-19 in the first two months after the second dose. After that, however, the number decreased by about 6 percent every two months and dropped to 83.7 percent after about four to six months.
However, the effectiveness of the vaccine against serious illnesses remained constant at around 97 percent.
“It’s not a huge drop, but it’s remarkable,” said Dr. Dean. “Overall, they found that the vaccine still works very well with a very high level of effectiveness.”
The study period ended before the advent of the Delta variant, the highly contagious version of the virus that is now dominant in the United States and makes vaccines a little less effective against infections.
The results come from 42,000 volunteers in six countries who participated in a clinical trial that Pfizer and BioNTech began last July. Half of the volunteers received the vaccine while the other half received a placebo. Both groups received two shots three weeks apart.
The researchers compared the number of people in each group who developed symptoms of Covid-19, which was then confirmed by a PCR virus test. When the companies announced their first results, the vaccine showed 95 percent effectiveness against symptomatic Covid-19.
In other words, the risk of disease was reduced by 95 percent in the group that received the vaccine compared to the group that received the placebo. That result – the first for a Covid-19 vaccine – brought the world a heady dose of hope in December as it rode the biggest wave of the pandemic.
Since then, the Pfizer BioNTech vaccine has made up the bulk of the vaccinations Americans have received, with more than 191 million doses administered to date, according to the Centers for Disease Control.
In the new study, researchers followed the volunteers for six months after vaccination through March 13. Over the entire period, the researchers estimated the effectiveness of the vaccine at 91.5 percent against symptomatic Covid-19. (The study did not measure the rate of asymptomatic viral infections.)
But over this period of time, the effectiveness gradually decreased. Between a week and two months after the second dose, it was 96.2 percent. In the period of two to four months after the vaccination, the effectiveness fell to 90.1 percent. From four months after vaccination to the March cutoff, it was 83.7 percent.
Understand the state of vaccine mandates in the United States
However, those numbers still describe a remarkably effective vaccine and may not convince critics that booster vaccination is widespread.
Earlier Wednesday, Pfizer reported that a third dose of its vaccine significantly increased blood levels of antibodies to several versions of the virus, including the Delta variant.
The results were similar for antibodies produced against the original virus and the beta variant first identified in South Africa. Pfizer and BioNTech expect to release more definitive research results in the coming weeks.
The announcement was a preliminary snapshot of data contained in an income statement. The results were neither peer-reviewed nor published in a scientific journal. And while antibody levels are an important measure of immunity, they’re not the only metric. The body has other defense mechanisms to fight off infection.
Pfizer also said in its statement that vaccines for children ages 5-11 could be available by the end of September. The vaccine is already approved in the USA for everyone aged 12 and over.
Pfizer’s vaccine had sales of $ 7.8 billion in the past three months, the company said and is well on its way to grossing more than $ 33.5 billion this year.
The vaccine is said to have more sales than any other medical product in a single year, and by a long way. The sales figures will bring the drug manufacturer a profit in the billions.