- New research has found that COVID-19 mRNA vaccines provide immunity for at least 6 months.
- But because COVID-19 is so new, experts are not sure whether immunity will decrease after that.
- Experts say more research will have to be done to understand whether people will need regular booster doses for COVID-19.
The COVID-19 vaccines produced by Pfizer and Moderna are highly effective in preventing COVID-19 cases in real-world conditions, and research suggests that they should remain effective over time.
What remains unclear, however, is exactly how long vaccines prevent COVID-19, whether booster vaccines may be needed in the future, or whether vaccines will need to be adjusted to fight emerging variants of the virus.
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They found that messenger RNA (mRNA) vaccines developed by pharmaceutical companies Pfizer-BioNTech and Moderna prevented 80 percent of cases after the first dose and 90 percent after the second dose.
Frontline workers in the study were tested for COVID-19 every week for 13 weeks.
The researchers said the shortage of positive COVID-19 tests in the study group indicates that vaccines reduce the risk of transmission of SARS-CoV-2 by vaccinated individuals to others.
“Reducing the risk of communicable infection, which can occur between people with asymptomatic infection or between people several days before the onset of symptoms, is especially important among health professionals, first responders and other essential and frontline professionals, given its potential for transmit the virus through close contact with patients and the public, ”noted the report.
“There is more and more evidence showing that … the transmission of the virus after vaccination is probably very low,” Dr. Susan Bailey, an allergist, immunologist and president of the American Medical Association, told Healthline.
Separately, Pfizer-BioNTech said the ongoing phase 3 clinical trial of its mRNA vaccine shows that strong immunization persists for at least 6 months among vaccinated individuals.
The researchers found that the vaccine was 100 percent effective against serious illnesses, as defined by the CDC, and 95.3 percent, effective against severe COVID-19, as defined by the Food and Drug Administration (FDA).
The vaccine has also been shown to be 100 percent effective against one of the main variants of COVID-19 (known as B.1.351) that currently circulates widely in South Africa.
A study that included 12,000 vaccinated individuals also found “no serious safety concerns” with the Pfizer-BioNTech vaccine, the companies announced.
“The good news is that in Pfizer’s 6-month status report, immunity remains very strong and we anticipate that it will continue to be strong,” said Bailey.
“Those people [in the study] have had the vaccine for the longest time, and that tells us that it lasts at least 6 months, ”added Bailey. “But it’s definitely longer than that – it’s not going to just drop after 6 months. I would have been concerned if the effectiveness had dropped by a third or half. ”
The fact that the effectiveness of the COVID-19 vaccine remained almost unchanged during the study period is an indication that the protection will last.
Bailey noted that some vaccines, such as measles, mumps and rubella, usually confer lifelong immunity. Others, like the flu vaccine, require a new injection each year.
“We don’t know which field the COVID-19 vaccine will fit into,” she said. “If we need a booster injection for COVID-19, we know it will be easy to produce” thanks to the new mRNA technology, she added.
Bailey said the vaccines in use appear to be effective against the COVID-19 variants that circulate in the United States. But, as the coronavirus continues to mutate, more resistant variants may emerge.
“My prediction is that a situation in which we would need a booster injection in the future is not because the first dose of the vaccine is gone, but because there is a new variant that may arise,” she said.
As noted in the research, vaccines do not completely eliminate the risk of developing COVID-19.
A recent report on 100 cases of COVID-19 that occurred in vaccinated people in Washington state raised some public alarm.
But experts say these “revolutionary” cases are to be expected and represent only a fraction of the more than 1 million Washington residents who have been vaccinated.
“Finding evidence of advanced vaccine cases reminds us that even if you have been vaccinated, you still need to wear a mask, practice social detachment and wash your hands to prevent the spread of COVID-19 to others who have not been vaccinated ”Said Dr. Umair A. Shah, Washington’s secretary of health.