On Thursday, Pfizer released updated clinical trial data that revealed that the COVID-19 vaccine is still very effective six months after volunteers from clinical trials were vaccinated.
In a rush for a viable vaccine for the public, biopharmaceutical companies could not initially guarantee how long immunity to COVID-19, the disease caused by the coronavirus SARS-CoV-2, would last. Now, Pfizer can confirm that immunity lasts at least six months for its two-stroke mRNA vaccine.
The question of how long SARS-CoV-2 vaccine immunity lasts was a bit of a mystery. Those infected with COVID-19 retain their immunity for only 3 to 12 months, studies have shown – a condition known as ‘transient immunity’, which means temporary, as opposed to a prolonged ‘lasting immunity’ . Vaccinations can confer different types of immunity as an infected infection, but because SARS-CoV-2 is a new virus, scientists were not sure how long vaccinated immunity would last. The new clinical trial data are encouraging for public health.
The findings come from an ongoing review of late-stage volunteers from the vaccine, and whether or not they developed COVID-19 with symptoms. The analysis examined the efficacy of the vaccine among 46,307 people enrolled in the Phase 3 study, as of July. Of the 927 cases of symptomatic COVID-19 cases from the clinical trial group, 850 of the cases came from people who received a placebo; 77 cases were of those vaccinated.
This means that up to six months after receiving the second shot, the vaccine still has 91.3 percent of the vaccine’s effectiveness, and 100 percent of the vaccine’s effectiveness in preventing serious diseases, as defined by the U.S. Centers for Disease Control and Prevention. (CDC). A further analysis found that the vaccine was also 100 percent effective in preventing COVID-19 cases in South Africa, where the dangerous B.1.351 variant is now the dominant strain.
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“This is an important step in further affirming the strong efficiencies and good safety data we have seen so far, especially in a long-term follow-up,” Ugur Sahin, CEO and co-founder of BioNTech, said in a press release. . “These data also provide the first clinical results that can effectively protect a vaccine against variants currently in circulation, a critical factor in achieving herd immunity and ending this pandemic for the world population.”
In particular, the data collected do not indicate any serious safety concerns. In general, adverse reactions in participants older than 16 include injection site pain (84.1%), fatigue (62.9%), headache (55.1%), muscle aches (38.3%), chills (31, 9%), joint pain (23.6%), fever (14.2%), swelling 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 announcement, Pfizer and BioNTech announced Wednesday that the vaccine is 100 percent effective in children ages 12 to 15, according to recent clinical trial data. Currently, the vaccine has so far only been approved for use on people over 16 years of age.
In general, it remains unclear how long the immunity lasts after receiving the Pfizer vaccine. As mentioned earlier, current science estimates that coronavirus immunity lasts only 3 to 12 months. But that does not mean that the vaccine will not be more durable than estimated. Booster shots could become a normal measure of public health in the next few years.
“The information coming from Pfizer-BioNTech is good news with evidence that those enrolled in the clinical trials last year are still protected. We therefore know that immunity will not be short-lived,” said Dr. Peter Hotez, a vaccination expert and dean of the School of Tropical Medicine at Baylor College of Medicine, told CNN. “Hopefully the protection can last for years, but we will not know until we know.”