Biopharmaceutical company Pfizer announced on Wednesday (Jul 28) that a third shot of its Covid-19 vaccine could improve immunity against the virus. However, two doses offer “lasting and robust protection” against serious diseases.
The new data released by Pfizer shows that levels of antibodies that can target the more transmissible Delta variant increases up to fivefold in individuals aged between 18 and 55 years old who receive a third dose of its Pfizer-BioNTech vaccine.
Furthermore, the study showed antibody levels grow 11-fold among those aged 65 to 85.
The findings were based on a test on 23 individuals released by Pfizer. It has not yet been peer-reviewed or published in a journal.
Pfizer suggested that a third dose of the vaccine could improve immunity, although the need for booster shots is far from settled, reported The New York Times.
The subject of booster shots is being debated among scientists, with health experts questioning its priority when many of the population have not yet received the first dose.
The United States Centers for Disease Control and Prevention notes that the current vaccines protect people against all common Covid-19 variants.
It is also unclear if increased antibody levels directly imply better protection.
“Receiving a third dose more than six months after vaccination, when protection may be beginning to wane, was estimated to potentially boost the neutralizing antibody titers in participants in this study to up to 100 times higher post-dose three compared to pre-dose three,” said Dr Mikael Dolsten.
Dr Dolsten leads worldwide research, development and medical for Pfizer.
“These preliminary data are very encouraging as Delta continues to spread,” he noted.
Pfizer and BioNTech also released new safety and efficacy data on their vaccine on Wednesday, noting protection holds up for at least six months but could begin to decline towards the end of the stated period.
The pre-print findings were based on a trial involving 44,000 volunteers worldwide.
The vaccine’s efficacy peaked at more than 96 per cent beginning one week to around two months after the second dose. It eventually declined to about 83.7 per cent four to six months later, showing an average decline rate of about six per cent over the last two months.
“We are in ongoing discussions with regulatory agencies regarding a potential third-dose booster of the current vaccine and, assuming positive results, anticipate an emergency use authorization submission as early as August,” said Dr Dolsten.
A lab study released on Sunday (Jul 25) from Chinese researchers noted that antibodies triggered by the Sinovac vaccine decline below a key threshold from around six months after the second dose. A third shot could be necessary for a strong boosting effect.
Chinese researchers noted that the fully vaccinated participants who had followed the two- or four-week interval between each dose showed a 16.9 per cent and 35.2 per cent level of neutralizing antibodies above the threshold six months after the second dose. /TISG
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