A coronavirus vaccine candidate developed by the Chinese Academy of Sciences (CAS) was shown to be safe in early and intermediate-stage studies and triggered immune responses, researchers said on Tuesday.
Last month in China began a late-stage study of the vaccine ZF2001, which CAS is developing with a unit of Chongqing Zhifei Biological Products. The aim is to recruit 29,000 people in China, Uzbekistan, Indonesia, Pakistan and Ecuador.
The candidate did not cause serious adverse events with common mild side effects such as injection pain, redness and swelling, researchers from the Chongqing Zhifei Department, CAS and other Chinese institutes said in an article published the Tuesday before the review.
The combined data from Phase 1 and 2 studies included 950 healthy Chinese participants aged 18 to 59 years. Low and high dose versions were tested, and the Phase 2 study also tested two doses versus three doses for both the low and high dose versions.
The higher dose, given over three injections 30 days apart, did not induce an improved immune response compared to the lower dose, the paper says. The Phase 3 study will study the lower-dose version, which was given via three injections.
Neutralizing antibodies to the virus were detected in at least 93% of participants who received three shots in different groups. The levels of antibodies raised by vaccines were higher than in samples from patients who had recovered from the disease, researchers said.
However, these antibody-based readings alone are insufficient to predict how effective ZF2001 will be in protecting people from the virus, the researchers said, warning they may not yet determine the duration of immune responses.
The vaccine also elicited moderate cell-based immune responses, a crucial part of the human immune system that works differently than antibodies.
ZF2001 is a vaccine against protein subunits, in which a harmless piece of the SARS-CoV-2 virus is used instead of the entire germ.
Four other Chinese vaccines from Sinopharm, Sinovac Biotech and CanSino Biologics have also entered phase 3 clinical trials.