Serologic Survey of Pandemic (H1N1) 2009 Virus, Guangxi Province, China

Sensitivity and Specificity of Serologic Assays for Detection of Human Infection with 2009 Pandemic H1N1 Virus in U.S. Populations

“…Studies from China and Singapore found little evidence of preexisting 2009 H1N1 virus cross-reactive antibodies in older adults, even those Ն80 years of age, suggesting that there are geographic or other factors that contribute to the presence of preexisting antibody in human populations (3,5,27). These findings support the need for laboratories undertaking seroepidemiological or seroprevalence studies for detection of antibody against novel viruses to individually evaluate the prepandemic age-specific prevalence of cross-reactive antibody in local populations.…”

“…HI titers (ranging from 5 to 640) and MN titers were transformed to log 2 . To best determine the relationship between HI and MN titers and to observe the proportion of variation in the MN titers that can be explained by HI titers, the following independent variables were included in the model: log 2 HI titer, log 2 HI titer 2 , and log 2 HI titer 3 . An age variable was not included in the model, as the majority of the rRT-PCR-confirmed sampled population had ages that ranged between 10 and 29 years.…”

Seroprevalence to Influenza A(H1N1) 2009 Virus—Where Are We?

“…Similar patterns were found in Italy (30), Taiwan (18), New Zealand (5), and Australia (26), with over 60% of samples being positive in some cohorts older than 85 years (13). In contrast, in Singapore and Hong Kong, the baseline seroprevalence in all age groups was equal to or below 5% (9,38), and in China no preexisting antibodies could be shown in rural farmers aged over 60 years (8). However, in Taiwan, 36% of nationwide serum samples from people over 75 years old had preexisting antibodies (18).…”

Immunogenicity and Safety of the Influenza A/H1N1 2009 Inactivated Split-Virus Vaccine in Young and Older Adults: MF59-Adjuvanted Vaccine versus Nonadjuvanted Vaccine

“…Allowing for the lack of preexisting antibodies cross-reactive with the novel influenza A (H1N1) virus, a two-dose vaccination was recommended for a protective antibody response in the early stage of the 2009 pandemic (3,11,26). Actually, in this study, even among the elderly aged Ն65 years, Ͻ10% of the study subjects had antibody titers of Ն1:40 at baseline, contrary to some reports from western countries; for example, Hancock et al (9) reported that 34% (39 of 115 persons) born before 1950 had HI titers of Ն80.…”