Hong Kong scientists urge third shot after study on new strain

HONG KONG • Researchers in Hong Kong have urged people to get a third dose of a Covid-19 vaccine as soon as possible, after a study showed insufficient antibodies were generated by the Sinovac and BioNTech products to fend off Omicron.

The results of a study, released on Tuesday, by scientists in the microbiology department of the University of Hong Kong was the first published preliminary data on the impact of Sinovac's vaccine against the Omicron variant of the coronavirus.

None of the serum of the 25 CoronaVac vaccine recipients contained sufficient antibodies to neutralise the new variant, according to the study, accepted for publication in the Clinical Infectious Diseases journal.

Just five of 25 BioNTech vaccine recipients had a neutralising ability against Omicron, and vaccine efficiency was reduced significantly to 20 per cent to 24 per cent, the study found.

"The public is advised to get a third dose of the vaccine as soon as possible while waiting for the next generation of a more matched vaccine," the researchers said.

The study, funded by the Hong Kong government, was carried out by microbiologists Yuen Kwok-yung, Kelvin To and Chen Honglin.

A Sinovac spokesman said its own laboratory testing showed a third dose of its vaccine was effective in producing Omicron antibodies. BioNTech did not immediately respond to questions on the study.

To keep new infections at bay, Hong Kong maintains one of the world's most stringent Covid-19 travel restrictions.

The United States and Britain this week joined South Africa and several other African nations on the list of countries for which government quarantine is required. People arriving from those countries now have to spend a week in an isolation camp at Penny's Bay Quarantine Centre, before serving out another 14 days in a hotel room they pay for themselves.

Separately, a US study released on Tuesday showed all three US-authorised Covid-19 shots appear to be significantly less protective against the Omicron variant in laboratory testing, but a booster dose likely restores most of the protection.

The study from researchers at Massachusetts General Hospital, Harvard and Massachusetts Institute of Technology that has not yet been peer reviewed tested blood from people who received the Moderna, Johnson & Johnson (J&J) and Pfizer-BioNTech vaccines against a pseudovirus engineered to resemble the Omicron variant.

The researchers found "low to absent" antibody neutralisation of the variant from the regular regimens of all three vaccines - two shots of the Moderna or Pfizer vaccines or one of J&J's single-dose vaccine. But the blood from recent recipients of an additional booster dose exhibited potent neutralisation of the variant, the study found.

The scientists suggested that Omicron is more infectious than previous variants of concern, and about twice as transmissible as the dominant Delta variant.

The results are in line with other studies recently published. Researchers at the University of Oxford said on Monday that they found the two-dose Pfizer and AstraZeneca Covid-19 vaccine regimens do not induce enough neutralising antibodies against Omicron.

Pfizer and BioNTech said last week that a three-shot course of their Covid-19 vaccine was able to neutralise the new variant in a laboratory test, but that two doses resulted in significantly lower neutralising antibodies.

Moderna and J&J have yet to release any of their own data about how the vaccines perform against Omicron. J&J declined to comment and Moderna did not respond.

REUTERS