BEIJING, Dec 23 (Reuters) - A coronavirus vaccine candidate
developed by the Chinese Academy of Sciences (CAS) was found to
be safe and triggered immune responses in early and mid-stage
trials, researchers said on Tuesday.
A late-stage trial of the ZF2001 vaccine, which CAS is
developing with a unit of Chongqing Zhifei Biological Products
, began last month in China. It aims to recruit
29,000 people across China, Uzbekistan, Indonesia, Pakistan and
The candidate did not cause serious adverse events, with
common mild side-effects including injection pain, redness and
swelling, researchers at the Chongqing Zhifei unit, CAS, and
other Chinese institutes said in a paper published on Tuesday
ahead of peer review. https://bit.ly/3nKZzt0
The combined data from Phase 1 and 2 trials involved 950
healthy Chinese participants aged 18-59. Low dose and high dose
versions were tested, and the Phase 2 study also tested two
doses versus three doses for both the low dose and high dose
The higher dose given via three injections spaced 30 days
apart did not induce an improved immune reponse compared to the
lower dose, the paper said. The Phase 3 trial will look at the
lower dose version given over three injections, it said.
Neutralising antibodies against the virus were detected
among at least 93% participants who received three shots in
different groups. The levels of vaccine-triggered antibodies
were higher than those seen in samples of patients recovered
from the disease, researchers said.
However, these antibody-based readings are on their own not
sufficient to predict how effective ZF2001 will be in protecting
people from the virus, researchers said, warning they could not
yet determine the duration of immune responses.
The vaccine also triggered moderate cell-based immune
responses, a crucial part of the human immune system that works
differently from antibodies.
ZF2001 is a protein subunit vaccine, which uses a harmless
piece of the SARS-CoV-2 virus rather than the entire germ.
Four other Chinese vaccines from Sinopharm, Sinovac Biotech
and CanSino Biologics have also entered Phase
3 clinical trials.
(Reporting by Roxanne Liu and Ryan Woo; Editing by Edwina