Vaccine effectiveness of two and three doses of BNT162b2 and CoronaVac against COVID-19 in Hong Kong

Abstract

Background: Hong Kong maintained extremely low circulation of SARS-CoV-2 until a major community epidemic of Omicron BA.2 starting in January 2022. Both mRNA BNT162b2 (BioNTech/Fosun Pharma) and inactivated CoronaVac (Sinovac) vaccines are widely available, however coverage has remained low in older adults. Vaccine effectiveness in this predominantly infection-naive population is unknown. Methods: We used individual-level case data on mild/moderate, severe/fatal and fatal hospitalized COVID-19 from December 31, 2021 to March 8, 2022, along with census information and coverage data of BNT162b2 and CoronaVac. We used a negative binomial model, adjusting for age and calendar day to estimate vaccine effectiveness of one, two and three dose schedules of both vaccines, and relative effectiveness by number of doses and vaccine type. Findings: A total of 12.7 million vaccine doses were administered in the 7.3 million population of Hong Kong, and we analyzed data from confirmed cases with mild/moderate (N=5,474), severe/fatal (N=5,294) and fatal (N=4,093) COVID-19. Two doses of either vaccine protected against severe disease and death, with higher effectiveness among adults ≥60 years with BNT162b2 (VE: 88.2%, 95% confidence interval, CI: 84.4%, 91.1%) compared to CoronaVac (VE: 74.1%, 95% CI: 67.8%, 79.2%). Three doses of either vaccine offered very high levels of protection against severe outcomes (VE: 98.1%, 95% CI: 97.1%, 98.8%). Interpretation: Third doses of either BNT162b2 or CoronaVac provide substantial additional protection against severe COVID-19 and should be prioritized, particularly in older adults who received CoronaVac primary schedules. Longer follow-up is needed to assess persistence of different vaccine platforms and schedules.

Effectiveness of an Inactivated Covid-19 Vaccine with Homologous and Heterologous Boosters against Omicron in Brazil

“…23 For the Omicron period, our estimates are consistent with an ecological study from Hong Kong regarding the effectiveness of a primary vaccination with CoronaVac. 12 However, our estimates of vaccine effectiveness against severe disease for a homologous booster are lower than reported the study in Hong Kong. The differences in study design, previous attack rate in the population, time of follow-up, non-pharmaceutical interventions in place during the Omicron outbreak in Hong Kong, and limited sample size for severe disease in the Hong Kong study could explain these differences.…”

“…The differences in study design, previous attack rate in the population, time of follow-up, non-pharmaceutical interventions in place during the Omicron outbreak in Hong Kong, and limited sample size for severe disease in the Hong Kong study could explain these differences. 12 There was evidence for waning of effectiveness against mild disease for homologous and heterologous boosters, and against severe disease for a homologous booster dose after three months during the Omicron period. This finding is consistent with numerous studies of primary series vaccination, [4][5][6] and with more recent studies of booster dose effectiveness over time.…”

“…11 Large Omicron epidemics associated with severe cases and deaths have been occurred in regions, most recently Eastern Asia, where inactivated vaccines have been extensively administered. 12 Brazil initiated booster vaccination in September 2021, after Delta VoC began to dominate in the country and three months before Omicron dominance. 5 Evidence concerning the effectiveness of inactivated vaccines with homologous or heterologous boosters is critically needed to inform vaccine policies in countries that used these vaccines in their initial rollout.…”

Emerging SARS-CoV-2 variants: Why, how, and what's next?

“…The effectiveness of Paxlovid and Molnupiravir indicate that the nsps are ideal targets for developing antiviral drugs, the activity of which are almost unaffected by spike mutations. Besides, the third dose of vaccines, based on the original SARS-CoV-2 Spike, can still significantly improve the immunity against Omicron 41 , 99 , 100 . Meanwhile, the spike-sequence-updated vaccines and pan-coronavirus vaccines are around the corner 101 , 102 , 103 .…”

COVID-19 vaccine booster strategy: striving for best practice

“… 7 Because the results reported by Jara and colleagues 1 do not cover the omicron surge, we cannot estimate the effectiveness of the three-dose schedules in those settings. McMenamin and colleagues 8 analysed the data from Dec 31, 2021, to March 8, 2022, to estimate the vaccine effectiveness of BNT162b2 and CoronaVac vaccines covering the fifth wave of COVID-19 with omicron BA.2 lineage in Hong Kong. Three doses of both vaccines were shown to be highly protective against severe disease and mortality in all age groups, yet the effects of heterologous vaccination have not been investigated.…”