On Thursday, Pfizer released updated clinical trial data that revealed that six months after the trial volunteers were inoculated, their COVID-19 vaccine remains highly effective.
In the rush to bring a viable vaccine to the public, biopharmaceutical companies were initially unable to guarantee how long their immunity against COVID-19, a disease caused by the SARS-CoV-2 coronavirus, would last. Now, Pfizer can confirm that immunity lasts at least six months for its two-dose mRNA vaccine.
The question of how long immunity to the SARS-CoV-2 vaccine lasts has been somewhat mysterious. Those infected with COVID-19 maintain their immunity for only 3 to 12 months, studies show – a condition known as “transient immunity”, which means temporary, as opposed to long-lasting “immunity”. Vaccines can confer different types of immunity than an eliminated infection, but since SARS-CoV-2 is a new virus, scientists were not sure how long the vaccinated immunity would last. The new data from clinical trials are encouraging for public health.
The findings come from an ongoing review of how volunteers for the final stage vaccine test are doing and whether they contracted COVID-19 with symptoms or not. The analysis examined the effectiveness of the vaccine in 46,307 people enrolled in the Phase 3 trial, which started in July. Of the 927 symptomatic cases of COVID-19 in the clinical trial group, 850 of these cases came from people who received a placebo; 77 cases were vaccinated.
This means that the vaccine still has 91.3 percent of the vaccine’s effectiveness rate up to six months after receiving the second injection and 100 percent of the vaccine’s effectiveness in preventing serious diseases, as defined by the Centers for Disease Control and Prevention. of the United States (CDC). Further analysis found that the vaccine was also 100 percent effective in preventing cases of COVID-19 in South Africa, where the dangerous variant B.1.351 is now the dominant strain.
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“It is an important step to further confirm the strong effectiveness and good safety data that we have seen so far, especially in a long-term follow-up,” said Ugur Sahin, CEO and co-founder of BioNTech, in a press release. “These data also provide the first clinical results that a vaccine can effectively protect against variants currently in circulation, a critical factor in achieving herd immunity and ending this pandemic for the global population.”
Notably, the data collected did not show serious safety concerns. Overall, adverse reactions in participants over 16 years old include pain at the injection site (84.1%), fatigue (62.9%), headache (55.1%), muscle pain (38.3 %), chills (31.9%), joint pain (23.6%), fever (14.2%), edema at the injection site (10.5%), redness at the injection site (9.5 %), nausea (1.1%), malaise (0.5%) and lymphadenopathy (0.3%).
In a separate ad, Pfizer and BioNTech announced on Wednesday that the vaccine is 100 percent effective in children aged 12 to 15, according to data from recent clinical trials. Currently, the vaccine is only authorized for use, so far, on an emergency basis, for people over 16 years old.
Overall, how long immunity lasts after receiving the Pfizer vaccine is still unclear. As mentioned earlier, current science estimates that immunity to coronavirus lasts only 3 to 12 months. But that does not mean that the vaccine will not be more durable than that estimate. Still, booster injections could become a normal public health measure in the years to come.
“The information from Pfizer-BioNTech is good news with evidence that those enrolled in clinical trials last year are still protected. So we know that immunity will not be short-lived,” Dr. Peter Hotez, vaccine specialist and dean the school of tropical medicine at Baylor College of Medicine, he told CNN. “Hopefully, protection can last for years, but we won’t know until we know.”