Study registration: *
Publication Kang M, SSRN, 2021
Dates: 2021-05-21 to 2021-06-23
Funding: Public/non profit (The National Natural Science Foundation of China and the Key-Area Research and Development Program of Guangdong Province)
Conflict of interest: no COI (We declare no competing interests.)

Methods

Study design:Cohort
Description of participants: Close contacts of confirmed COVID cases during an outbreak in China
Inclusion criteria:
  • Individuals identified as close contacts of COVID-19 cases by public health authorities in the Guangdong outbreak - defined as all individuals who lived in the same household or stayed in the same public space without protection within close distance within up to four days before illness onset for symptomatic cases, or were identified by the first positive specimen for asymptomatic cases.

Exclusion criteria:
  • Missing basic demographic information
  • received two doses of vaccine but less than 21 days apart
  • younger than 18 years

Follow-up duration (months): 1
Vaccines:
  • 1 or 2 doses of HB02 or WIV04 or CoronaVac or BICV
Variant description :
Variant name: Delta
Evidence: Direct evidence (effectiveness determined by sequencing cases)
Documents
available

Protocol

NR

Statistical plan

NR

Data-sharing stated: Yes
Data accessibility: Individual-level data will not be made publicly available with this article. Requests for sharing of deidentified individual-level data for scientific research can be directed to Min Kang: kangmin@yeah.net
General comment We have concerns about uncontrolled confounding (due to the observational nature of the data) and about selection bias due to how participants were selected.