Title:
A rubella outbreak investigation and BRD-II strain rubella vaccine effectiveness study, Harbin city, Heilongjiang province, China, 2010-2011.

Abstract:
In the 1990s, China introduced rubella vaccine into the private market using BRD-II virus strain, which is different than the globally used RA27/3 strain. In 2007, BRD-II rubella containing vaccine was introduced into the national immunization program and recommended for routine use. However, to our knowledge, there are no field vaccine effectiveness (VE) studies of BRD-II rubella vaccine. In April 2011, a rubella outbreak was detected in two daycare centers in Harbin city, China. We conducted an investigation to determine VE of BRD-II rubella vaccine.
Rubella cases were either laboratory-confirmed or epidemiologically linked to laboratory-confirmed cases. We collected demographic characteristics, migrant status, and history of rubella and measles vaccination from all children in the two daycare centers.
The first case of rubella was on 22 November, 2010. Among the 143 children in the two daycare centers, 22 acquired rubella, for an overall attack rate (AR) of 15.4% (22/143). The AR in higher-grade classes (21.7%) was higher than in lower grade classes (3.9%). The AR among migrant children (47.8%) was higher than among local children (9.2%). Rubella vaccine coverage was 17% (24/143), while measles vaccine coverage was 100%. The AR among rubella-vaccinated children was 0% (0/24), and the AR among rubella-unvaccinated children was 18.5% (22/119), for a VE of 100% (P value=0.025, 95% CI: 35-100%). Rubella vaccine coverage among children born before 2007 was 10.2% (10/98), and was lower than that for children born in 2007 or after (31.1% (14/45), RR=0.33, 95%CI: 0.16-0.68). Emergency vaccination was conducted on 11 and 12 April 2011, and the outbreak stopped in one week later.
Domestic BRD-II strain rubella vaccine showed high vaccine effectiveness against rubella. Rubella vaccine coverage through routine immunization was insufficient. Consideration should be given for measuring rubella vaccine coverage to determine the need for catch-up vaccination in China.