The
real-world study, which has not been peer-reviewed, was based on a second dose
of the J&J vaccine administered to 69,092 workers between Nov 15 and Dec
20.
An initial
course of inoculation has been shown to offer only greatly reduced protection
against infection by omicron, which is spreading quickly through many countries
after first being identified in southern Africa and Hong Kong in late November.
However,
several studies have suggested that a booster dose provides significant
protection against severe illness from the variant.
The South
African study showed the J&J vaccine’s effectiveness at preventing
hospitalisation rose from 63 percent shortly after a booster was administered
to 84 percent 14 days later. Effectiveness reached 85 percent at one to two
months post-boost.
“It
reassures us that COVID-19 vaccines continue to be effective for the purpose
they were designed, which is to protect people against severe disease and
death,” said Linda-Gail Bekker, the study’s co-lead investigator.
“This
is yet another piece of evidence that we have not lost that impact even in the
face of a very mutated variant.”
Bekker said
the jury was “still out” on the issue of further boosters for the
J&J vaccine, which is administered as a single shot for the first full
dose, and which is easier to transport to remote African rural areas than the
rival, two-dose Pfizer mRNA vaccine due to better heat tolerance.
“What
we are showing is that two doses really restore full protection, and I don’t
think we can extrapolate from this that we are going to need a third or a
fourth boost at all.”
Researchers
said their analysis had several limitations, including short follow-up times.
Those averaged eight days for healthcare workers who had received their boost
within the previous 13 days, or 32 days for those boosted 1-2 months earlier.
In a company
statement, Mathai Mammen, global head at Janssen Research & Development,
said the firm believed protection could be due to robust T-cell responses
induced by the vaccine.
“Furthermore,
these data suggest that omicron is not affecting the T-cell responses generated
by our vaccine,” he said.
