China Study Identifies Few Serious AEs with H1N1 Vaccine

The outbreak of the pandemic influenza A (H1N1) virus in 2009 led nations around the world to produce a vaccine against the virus. During the summer of 2009, 10 Chinese vaccine manufacturers used the same reassortant strain X-179A (A/California/07/2009-A/PR/8/34) as the seed virus to produce various formulations of the vaccine. China began administering vaccines in priority populations in September 2009. Because vaccines can cause adverse events (AEs), researchers from the Chinese Center for Disease Control and Prevention (CDC) in Beijing conducted postmarketing surveillance of AEs.

During the initial H1N1 vaccination, in which nearly 90 million individuals in China were vaccinated from September 21, 2009, through March 21, 2010, passive surveillance for AEs was conducted. Reporting in the New England Journal of Medicine [2011;364(7):638-647], the researchers determined that AEs associated with the vaccine appeared to be limited and relatively rare. Furthermore, there was no evidence of an increased risk of Guillain-Barré syndrome. This study aimed to verify, analyze, and assess the safety of China’s vaccination program. Physicians or vaccination providers were required to report the numbers of vaccines and all AEs to their local CDC, which then reported the data to the Chinese CDC through the online National Immunization Information System’s National Adverse Event Following Immunization (AEFI) Surveillance System.

The researchers defined serious AEs as events involving hospitalization, death, life-threatening illness, or permanent disability. The priority population eligible for vaccination included individuals in frontline public services; students and teachers in preschools, elementary and middle schools, and high schools; individuals with chronic conditions; and other individuals at high risk for influenza A (H1N1) infection. All adults and children ≥3 years of age were eligible for 1 dose of vaccine containing 15