It’s the first look at how long protection will last for a coronavirus vaccine, and while six months is a humble goal, it’s longer than the 90 days that has been offered as the best estimate so far.
The vaccine remains more than 91% effective against diseases with symptoms for six months, the companies say. And it appeared fully effective against the worrying B.1.351 variant of the virus, which is the dominant strain in South Africa that researchers feared evolved to evade vaccine protection, the companies said.
“The vaccine was 100% effective against serious disease as defined by the US Centers for Disease Control and Prevention (CDC) and 95.3% effective against serious COVID-19, as defined by the US Food and Drug Administration (FDA) defines, “Pfizer and BioNTech said in a joint statement.
On Wednesday, the companies announced that a small study of volunteers ages 12-15 showed 100% effectiveness in this age group.
“These data confirm the favorable efficacy and safety profile of our vaccine and prompt us to file an application for a biologics license with the US FDA,” said Albert Bourla, chairman and CEO of Pfizer, in a statement. A BLA is an application for full approval. The vaccine currently has an Emergency Authorization (EUA), which is not fully approved.
“The high effectiveness of the vaccine, observed up to six months after a second dose and against the variant predominant in South Africa, gives further confidence in the overall effectiveness of our vaccine.”
The company has tested the vaccine on more than 46,000 volunteers and identified 927 cases of confirmed Covid-19.
“Of the 927 confirmed symptomatic cases of COVID-19 in the study, 850 cases of COVID-19 were in the placebo group and 77 cases were in the BNT162b2 group, giving the vaccine a 91.3% effectiveness,” it said.
“Thirty-two cases of serious illness, as defined by the CDC, were observed in the placebo group compared to none in the BNT162b2 vaccine group, indicating that the vaccine was 100% effective against serious illness by the CDC definition in this analysis One case as defined by the FDA was observed in the placebo group versus a case in the BNT162b2 vaccinated group, indicating 95.3% efficacy by the FDA definition. “
These definitions are important. The FDA’s definition of serious illness included an increased respiratory rate, indicative of shortness of breath; increased heart rate, an oxygen saturation level of 93% or less; Respiratory failure so severe that supplemental oxygen or ventilation is needed; a drop in blood pressure indicating shock; significant renal, hepatic, or neurological dysfunction, ICU admission, or death.
The definition of CDC includes blood oxygen levels of 94% or less and an x-ray finding of pulmonary infiltrates – an indication of pneumonia – greater than 50%
The most common adverse events were injection site pain, fatigue, and headache.
“In South Africa, where the B.1.351 line prevails and 800 participants were enrolled, nine cases of COVID-19 were observed in the placebo group, indicating a vaccine effectiveness of 100%,” the company said.
“Vaccine safety has now been examined in more than 44,000 participants aged 16 and over, with more than 12,000 vaccinated participants being examined for at least six months after their second dose.”
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