The makers of Russia’s second approved coronavirus vaccine EpiVacCorona are studying third doses to boost recipients' immune response, a senior scientist said Wednesday.
Approved last fall and added to Russia’s mass immunization program last month, EpiVacCorona has come under scrutiny after a group of late-trial study participants claimed that it does not produce an immune response. Early-trial results published in a Russian medical journal this spring disputed that claim, saying that all adults involved in phase one and two trials had developed antibodies.
Alexander Ryzhikov, head of zoonotic infections at the Siberia-based Vektor Institute that developed EpiVacCorona and co-author of the early-trial study, said triple vaccination tests on animals have “confirmed increased and prolonged immunity.”
“First and second-phase clinical trials to introduce triple vaccination [of humans] with this vaccine are currently underway,” Ryzhikov said.
Speaking at an Instagram forum hosted by Russia’s consumer protection watchdog Rospotrebnadzor, which leads national Covid-19 containment efforts, Ryzhikov called third vaccine doses “natural.”
“It is worthy of revaccination, possibly repeated double revaccination, by virtue of its harmlessness,” he added.
The scientist did not say how many trial subjects are involved in monitoring the third shot’s safety and efficacy. EpiVacCorona’s first phase trials involved 14 people and second placebo-controlled phase trials 86.
No peer-reviewed research on the two-shot peptide EpiVacCorona vaccine has been published yet, though Vektor says it has submitted proposals to a number of journals.
Western vaccine developers Pfizer and Moderna are also studying the effects of adding a third dose of their jabs to the vaccination regimen, with developers saying the jabs may become annual like flu shots.
President Vladimir Putin has been vaccinated with both doses of one of Russia’s three domestically manufactured Covid-19 vaccines. The Kremlin has not disclosed which jab Putin received.
While Putin has set the target of vaccinating nearly 70 million people to reach herd immunity by this summer, the country's vaccination program has been hampered by widespread public skepticism.