Case-Control Study of the Effectiveness of the 2010-2011 Seasonal Influenza Vaccine for Prevention of Laboratory-Confirmed Influenza Virus Infection in the Korean Adult Population

Abstract

We evaluated the effectiveness of the 2010-2011 seasonal influenza vaccine for preventing laboratory-confirmed influenza in a South Korean population. A retrospective case-control study was conducted among patients who visited selected hospitals from September 2010 to May 2011. A total of 483 laboratory-confirmed influenza patients were included in the analysis as case subjects. For each case patient, two types of control patients were chosen at a ratio of 1:1:1, and 966 control subjects were selected. Vaccine effectiveness (VE) was defined as 100 ؋ (1 ؊ odds ratio for influenza in vaccinated versus nonvaccinated persons). The VE of the 2010-2011 seasonal influenza vaccine was 49.5% to 45.8% for both influenza A and B viruses and 50.8% to 47.2% for influenza A virus, according to the control type. The age-specific adjusted VE was 50.8% to 46.5% among subjects aged 19 to 49 years and 58.7% to 63.3% among those aged 50 to 64 years, according to the control type. Statistically significant VE was not found among those aged >65 years or against influenza B virus. The 2010-2011 seasonal influenza vaccine was effective for preventing laboratory-confirmed influenza, especially for influenza A virus, in a South Korean population. Evidence of the effectiveness of the influenza vaccine in older adults or against influenza B virus was not found.

Suboptimal Effectiveness of the 2011–2012 Seasonal Influenza Vaccine in Adult Korean Populations

“…In addition, the vaccine did not demonstrate a statistically significant effectiveness for preventing influenza-related complications, including pneumonia, hospitalization or death. This finding was different from a previous study performed during the 2010–2011 season [ 8 ]. The main circulating influenza strain in the 2010–2011 season was the A/H1N1 2009pdm virus.…”

“…Therefore, to minimize the false negative results, control participants were restricted to patients who visited the same hospital with ILI within 48 hours of symptom onset. This type of control was proven to be appropriate in the previous study [ 8 ]. This method of control selection might cause another type of bias.…”

Prospective Cohort Study on the Effectiveness of Influenza and Pneumococcal Vaccines in Preventing Pneumonia Development and Hospitalization

“…Recently, the Spanish influenza surveillance system reported low VE in seasons with predominant circulation of influenza A/H3N2 (14). Similarly, in the ROK, circulation of influenza A/H3N2 was dominant in the past 3 years, with reportedly low influenza VE (15,16). Of note, this study showed that influenza vaccination would be beneficial for elderly individuals and those with comorbidities despite statistically insignificant influenza VE.…”

Effectiveness of COVID-19 vaccine in preventing infection and disease severity: a case-control study from an Eastern State of India

“…The case-control design is the cost-effective and rapid way of the VE assessment during epidemic situation [10]. Previously case control study designs have been used in the post-licencing effectiveness of the oral cholera vaccine, rota virus vaccine and the influenza vaccines [13][14][15]. The case control design has already been adopted by studies from other countries for the COVID-19 VE assessment [16][17][18].…”