WEDNESDAY, Nov. 18, 2020 — A Chinese COVID-19 vaccine seems to be safe and effective, early trial results suggest, but one expert says the findings should be regarded with caution.
The CoronaVac vaccine is based on inactivated SARS-CoV-2 virus. It was tested in a phase 1/2 clinical trial that included more than 700 healthy volunteers, ages 18-59, who were recruited in China between April 16 and May 5.
The vaccine appeared to be safe and well-tolerated at all tested doses, researchers reported. The most common reported side effect was pain at the injection site.
Even at the lowest dose tested (3 micrograms), participants had strong antibody responses within two weeks of the second and final dose. Shots were given 14 days apart.
Though levels of antibodies triggered by the vaccine were lower than those in recovered coronavirus patients, researchers said they still believe the vaccine could provide protection from the virus.
They noted that the trial’s primary objective was to evaluate the vaccine’s immune response and safety. It wasn’t designed to assess how effective the vaccine is in preventing infection with SARS-CoV-2.
The findings were published Nov. 17 in The Lancet Infectious Diseases journal.
After taking into account side effects and other factors, the researchers determined that a dose of 3 mcg prompted the highest antibody response. This will be investigated further in phase 3 trials now underway.
“Our findings show that CoronaVac is capable of inducing a quick antibody response within four weeks of immunization by giving two doses of the vaccine at a 14-day interval. We believe that this makes the vaccine suitable for emergency use during the pandemic,” said co-lead author Fengcai Zhu of the Jiangsu Provincial Center for Disease Control and Prevention in Nanjing, China.
“In the longer term, when the risk of COVID-19 is lower, our findings suggest that giving two doses with a one-month interval, rather than a two-week interval, might be more appropriate for inducing stronger and potentially longer-lasting immune responses. However, further studies are needed to check how long the antibody response remains after either vaccination schedule,” Zhu said in a journal news release.
CoronaVac is one of 48 COVID-19 vaccine candidates now in clinical trials.
Naor Bar-Zeev, an associate professor in the Division of Global Disease Epidemiology and Control at Johns Hopkins University in Baltimore, wrote an editorial that accompanied the findings.
“Like all phase 2 trials, the results must be interpreted with caution until phase 3 results are published,” he wrote. “But even then, after phase 3 trial completion and after licensure, we should prudently remain cautious.”
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