Veguilla Vic, López-Gatell Hugo, López-Martínez Irma, Aparicio-Antonio Rodrigo, Barrera-Badillo Gisela, Rojo-Medina Julieta, Gross Felicia Liaini, Jefferson Stacie N, Katz Jacqueline M, Hernández-Ávila Mauricio, Alpuche-Aranda Celia M
Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
Dirección General Adjunta de Epidemiología, Secretaría de Salud, Mexico City, México.
PLoS One. 2016 Mar 22;11(3):e0150428. doi: 10.1371/journal.pone.0150428. eCollection 2016.
The 2009 H1N1 influenza pandemic initially affected Mexico from April 2009 to July 2010. By August 2010, a fourth of the population had received the monovalent vaccine against the pandemic virus (A(H1N1)pdm09). To assess the proportion of the Mexican population who remained potentially susceptible to infection throughout the summer of 2010, we estimated the population seroprevalence to A(H1N1)pdm09 in a serosurvey of blood donors.
We evaluated baseline cross-reactivity to the pandemic strain and set the threshold for seropositivity using pre-pandemic (2005-2008) stored serum samples and sera from confirmed A(H1N1)pdm09 infected individuals. Between June and September 2010, a convenience sample serosurvey of adult blood donors, children, and adolescents was conducted in six states of Mexico. Sera were tested by the microneutralization (MN) and hemagglutination inhibition (HI) assays, and regarded seropositive if antibody titers were equal or exceeded 1:40 for MN and 1:20 for HI. Age-standardized seroprevalence were calculated using the 2010 National Census population.
Sera from 1,484 individuals were analyzed; 1,363 (92%) were blood donors, and 121 (8%) children or adolescents aged ≤19 years. Mean age (standard deviation) was 31.4 (11.5) years, and 276 (19%) were women. A total of 516 (35%) participants declared history of influenza vaccination after April 2009. The age-standardized seroprevalence to A(H1N1)pdm09 was 48% by the MN and 41% by the HI assays, respectively. The youngest quintile, aged 1 to 22 years, had the highest the seroprevalence; 61% (95% confidence interval [CI]: 56, 66%) for MN, and 56% (95% CI: 51, 62%) for HI.
Despite high transmission of A(H1N1)pdm09 observed immediately after its emergence and extensive vaccination, over a half of the Mexican population remained potentially susceptible to A(H1N1)pdm09 infection. Subsequent influenza seasons with high transmission of A(H1N1)pdm09, as 2011-2012 and 2013-2014, are compatible with these findings.
2009年甲型H1N1流感大流行最初在2009年4月至2010年7月期间影响了墨西哥。到2010年8月，四分之一的人口接种了针对大流行病毒（甲型H1N1流感病毒）的单价疫苗。为了评估2010年整个夏季仍有潜在感染易感性的墨西哥人口比例，我们在一项献血者血清学调查中估计了甲型H1N1流感病毒的人群血清阳性率。
我们评估了对大流行毒株的基线交叉反应性，并使用大流行前（2005 - 2008年）储存的血清样本以及确诊的甲型H1N1流感病毒感染个体的血清来设定血清阳性阈值。2010年6月至9月期间，在墨西哥的六个州对成年献血者、儿童和青少年进行了一项便利样本血清学调查。血清通过微量中和（MN）试验和血凝抑制（HI）试验进行检测，当MN抗体滴度等于或超过1:40且HI抗体滴度等于或超过1:20时被视为血清阳性。使用2010年全国人口普查数据计算年龄标准化血清阳性率。
对1484人的血清进行了分析；其中1363人（92%）为献血者，121人（8%）为年龄≤19岁的儿童或青少年。平均年龄（标准差）为31.4（11.5）岁，276人（19%）为女性。共有516名（35%）参与者宣称在2009年4月后有流感疫苗接种史。通过MN试验和HI试验测得的甲型H1N1流感病毒年龄标准化血清阳性率分别为48%和41%。年龄最小的五分之一人群，即1至22岁的人群，血清阳性率最高；MN试验为61%（95%置信区间[CI]：56，66%），HI试验为56%（95%CI：51，62%）。
尽管甲型H1N1流感病毒出现后立即观察到其高传播性以及广泛接种疫苗，但超过一半的墨西哥人口仍有感染甲型H1N1流感病毒的潜在易感性。随后的流感季节，如2011 - 2012年和2013 - 2014年甲型H1N1流感病毒的高传播情况与这些发现相符。
