Omicron vaccines to start clinical trials in HK

Three omicron-specific coronavirus disease 2019 (COVID-19) vaccine candidates will be evaluated in clinical trials in Hong Kong.

The inactivated vaccine candidates – one manufactured by Sinovac, two manufactured by China National Biotec Group (CNBG; a Sinopharm subsidiary) – received clinical trial approval in Hong Kong in mid-April ahead of their expected launch in mainland China this autumn.

According to a company press release, the Sinovac vaccine candidate is based on the Omicron variant first reported to WHO in November 2021. However, the press release did not contain details of the clinical trial to be conducted in Hong Kong. [http://www.sinovac.com/news/shownews.php?id=1448&lang=en]

The two CNBG vaccine candidates, based on a BA.1 seed supplied by the University of Hong Kong, will be evaluated as boosters in adults who have previously received two or three doses of a COVID-19 vaccine. [https://www.scmp.com/news/hong-kong/article/3174518/coronavirus-hong-kong-approves-clinical-trials-3-chinese-vaccines]

Approval of the clinical trials came amid Hong Kong’s fifth wave of COVID-19 outbreak driven by the Omicron variant. In early phases of the fifth wave, low vaccination rates resulted in an overwhelming number of cases requiring hospitalization and soaring death rates, especially among the older population. [BMJ 2022;doi:10.1136/bmj.o980; https://www.coronavirus.gov.hk/eng/5th-wave-statistics.html]

The high level of vaccine hesitancy in Hong Kong was related to a general lack of public trust in the government and failure of the vaccination campaign to counter misinformation about COVID-19 vaccine safety. Risk-benefit conversations about COVID-19 vaccines in the older population fell on the shoulders of physicians, many of whom were cautious about comparing the performance of the two available vaccines (mRNA-based BNT162b2 and inactivated CZ02) in case of being held liable for adverse effects. [BMJ 2022;doi:10.1136/bmj.o980]

Among older individuals in Hong Kong who are vaccinated, a sizeable proportion received CZ02, which is shown to be less effective than BNT162b2 in preventing hospitalizations and death in older adults, with a clear tendency of decreasing effectiveness with age. [https://www.covidvaccine.gov.hk/en/dashboard; Lancet Healthy Longev 2022;3:e242-e252]

In a qualitative study in older Chinese adults in Hong Kong, barriers to and hesitancy towards COVID-19 vaccination were found to be related to lack of trust and confidence in the vaccine and the government, perceptions of the vaccine as dangerous with poor long-term effectiveness, perceptions of being unsuitable for vaccination, peer pressure, fragile social networks, stigma towards healthcare workers, and perceptions of vaccines as toxic or viral injections. [BMC Geriatr 2022;doi:10.1186/s12877-022-03000-y]

Another study showed that older adults in Hong Kong tended to be less worried about COVID-19 infection and its impact on economic activity/livelihood, but slightly more worried about supplies of personal protective equipment, compared with younger adults. [BMC Geriatr 2022;doi:10.1186/s12877-022-03009-3]

Most COVID-19 deaths in Hong Kong’s 5th wave were among unvaccinated elderly.