(342) Effectiveness of BNT162b2 and CoronaVac in individuals with multimorbidity: a territory-wide case-control study

Background: Multimorbidity entails a higher risk of SARS-CoV-2 infection and COVID-19-related complications, yet previous studies showed that people with chronic conditions or multimorbidity may be hesitant towards COVID-19 vaccination. Research on potential benefits of vaccination specific to individuals with multimorbidity may reduce vaccine hesistancy, but available data is limited.

Objectives: To estimate the effectiveness of one, two and three doses of BNT162b2 or CoronaVac among individuals with and without multimorbidity during an Omicron outbreak.

Methods: A case-control study using territorywide electronic health records in Hong Kong. Multimorbidity was defined as having two or more of a list of 30 chronic conditions on or before index date. Cases of COVID-19 infection, hospitalization, and mortality were identified from January to March 2022. Each case was matched with up-to-10 controls by age, sex, outpatient attendance or hospitalization date, and Charlson Comorbidity Index. Conditional logistic regression adjusted for chronic conditions was used to estimate the association between different number of doses of BNT162b2/CoronaVac and the outcomes.

Results: 101427, 16675 and 5371 cases of COVID-19 infection, hospitalisation and mortality in individuals with multimorbidity; 411485, 17333, 2325 cases respectively in those without multimorbidity, were identified. Vaccine effectiveness against COVID-19 infection in those with multimorbidity after the first dose of BNT162b2 and CoronaVac were 31.5% (95%CI: 28.6-34.4) and 1.9% (0.3-4.0) respectively, with higher effectiveness observed after three doses [BNT162b2 58.8% (57.3-60.2), CoronaVac 29.4% (27.3-31.4)]. Vaccine effectiveness against COVID-19-related hospitalization and mortality in those with multimorbidity were 90.4% (88.9-91.8) and 97.9% (96.0-98.9) after three doses of BNT162b2 and 86.2% (84.5-87.7) and 94.9% (92.7-96.4) after three doses of CoronaVac respectively. Notably, vaccine effectiveness against COVID-19 infection was consistently greater in those with multimorbidity than those without, but the difference was less pronounced for hospitalisation and negligible for mortality.

Conclusions: Both BNT162b2 and CoronaVac were effective against COVID-19 infection, hospitalisation and mortality among individuals with multimorbidity during an Omicron outbreak, with booster dose offering higher levels of protection. Vaccine effectiveness against COVID-19 infection were consistently higher in those with multimorbidity than those without. Findings confirm the significant benefits of BNT162b2 and CoronaVac among people with more complex multimorbidity burden. Further vaccine roll-out should prioritize people with multimorbidity.