Two doses of the Johnson & Johnson (J&J) Covid-19 vaccine cut the risk of hospitalisation by up to 85 per cent, according to a South African study conducted when the Omicron coronavirus variant was dominant.
The findings of the real-world study, made public on Thursday and not yet peer-reviewed, provide a significant fillip to the J&J shot, widely used in South Africa and elsewhere.
The world is grappling with an explosion in coronavirus cases caused by the variant, which was first identified late last month in southern Africa. Some countries have recorded record-breaking numbers of infections, and the World Health Organisation has warned of a "tsunami of cases" caused by the concurrent circulation of the Delta and Omicron variants.
Linda Gail-Bekker, the director of the Desmond Tutu HIV centre and co-lead of the study, said she believed the Johnson & Johnson doses provided the “biggest numbers” on vaccine efficacy against Omicron so far.
Covid-19: Record 20,554 cases as isolation reduced to seven days for those with booster
Cabinet to consider shorter isolation for Covid cases and close contacts due to work absences
Boris Johnson defends decision not to impose fresh restrictions before new year
Gloom envelops hospitality and tourism sector at the end of 2021
“It is a big deal,” she told the Financial Times. “We were very anxious that a variant as ‘mutated’ as Omicron would render our current vaccines ineffective. These are early data but still very reassuring that our vaccines are holding up for the purpose they were designed for – to protect against severe disease and death.”
Single shot
The study, conducted on more than 69,000 healthcare workers, assessed the effectiveness of a booster shot of the vaccine, initially intended to be a single-shot inoculation, six to nine months after primary vaccination.
“This data is important given the increased reliance on the [J&J] vaccine in Africa,” the researchers wrote. Efficacy was highest about one to two months after the booster was received, they added.
Early evidence suggests Omicron causes less severe symptoms compared with previous variants, although observers have suggested this may be because large parts of the global population have already been exposed to coronavirus since it first emerged two years ago or because they have been vaccinated. It is unclear whether it is less severe for the unvaccinated or those who have never contracted the disease.
On Thursday the WHO warned against making premature conclusions on virulence, saying more data were needed and that its higher transmissibility could still cripple hospitals and economies.
Other, early and limited evidence made public so far suggests full courses of existing vaccines, including one dose of the J&J shot, are somewhat less effective against Omicron, eliciting diminished antibody responses and underscoring the need for boosters, which appear to restore some of the antibody loss seen in blood sample studies.
But, crucially, scientists still do not fully understand how antibody levels translate to efficacy against coronavirus, also because other parts of the immune response are protective against disease.
Ramped up
Richer countries have ramped up their booster programmes although access to vaccines remains unequal worldwide, with Financial Times analysis published this month finding that booster doses administered in richer countries outnumber all doses given in poorer nations.
Some drugmakers have begun tweaking their shots in cases Omicron-targeted vaccines are needed, though health authorities have warned it will take time to reach a consensus on whether they are needed.
J&J has said it would sell its vaccine at cost during the pandemic. – Copyright The Financial Times Limited 2021
