Preliminary assessment of the effectiveness of the 2003-04 inactivated influenza vaccine--Colorado, December 2003

Influenza activity started earlier than usual in the United States this season, with widespread influenza activity reported in 10 states by November 22, 2003. The predominant influenza viruses (A/Fujian/411/2002 [H3N2]-like viruses) circulating this season differ antigenically from the 2003-04 influenza A (H3N2) vaccine strain. A retrospective cohort study was conducted among workers at a Colorado hospital to provide preliminary data on the effectiveness of trivalent inactivated influenza vaccine (TIV) against influenza-like illness (ILI). This report summarizes the results of that study, which indicated that TIV had no or low effectiveness against ILI. However, additional studies are needed to evaluate the effectiveness of the 2003-04 vaccine against laboratory-confirmed influenza and influenza-related complications, including hospitalization and death. Influenza vaccine continues to be recommended, particularly for persons at increased risk for influenza-related complications, their household contacts, and health-care personnel.     

Efficacy of trivalent, cold-adapted, influenza virus vaccine against influenza A (Fujian), a drift variant, during 2003-2004

In the 2003-2004 influenza season, the predominant circulating influenza A (H3N2) virus in the United States was similar antigenically to A/Fujian/411/2002 (H3N2), a drift variant of A/Panama/2007/99 (H3N2), the vaccine strain. That year, a field study of trivalent live-attenuated influenza vaccine (LAIV-T) was conducted in Temple-Belton, Texas, as part of a larger community-based, non-randomized, open-label study in three communities that began in August 1998 [Gaglani MJ, Piedra PA, Herschler GB, Griffith ME, Kozinetz CA, Riggs MW, et al. Direct effectiveness of the trivalent, cold-adapted, influenza virus vaccine (CAIV-T) against the 2000-2001 influenza A (H1N1) and B epidemic in healthy children. Arch Pediatr Adolesc Med 2004;158:65-73; Piedra PA, Gaglani MJ, Kozinetz CA, Herschler G, Riggs M, Griffith M, et al. Herd immunity in adults against influenza-related illnesses with use of the trivalent-live attenuated influenza vaccine (CAIV-T) in children. Vaccine 2005;23:1540-8; Piedra PA, Gaglani MJ, Riggs M, Herschler G, Fewlass C, Watts M, et al. Live attenuated influenza vaccine, trivalent, is safe in healthy children 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age in a community-based, nonrandomized, open-label trial. Pediatrics 2005;116:397-407]. Participants were healthy children aged 5-18 years. The analysis here concerns 6403 children in the Scott & White Health Plan (SWHP) database living within zip codes of the Temple-Belton area, of whom 1706 received LAIV-T and 548 received trivalent inactivated vaccine (TIV) in 2003, 983 had been previously vaccinated in 1998-2001, but not in 2002-2003 or 2003, and 3166 had never been vaccinated. The main outcome measure was medically-attended acute respiratory illness (MAARI). Surveillance culture results were incorporated into the analysis to estimate efficacy against culture-confirmed influenza illness. Vaccine effectiveness of LAIV-T against MAARI was 26% (95% confidence interval (CI) 11, 39). Vaccine efficacy of LAIV-T against culture-confirmed influenza illness including surveillance cultures of children in the SWHP database in the validation calculation was 56% (95% CI 24, 84). LAIV-T was cross-protective with a drift variant strain in 2003-2004, evidence that such vaccines could be important for preparing for a pandemic and for annual influenza.     

Update: influenza activity--United States and worldwide, 2003-04 season, and composition of the 2004-05 influenza vaccine

During the 2003-04 influenza season, influenza A (H1), A (H3N2), and B viruses co-circulated worldwide, and influenza A (H3N2) viruses predominated. Several Asian countries reported widespread outbreaks of avian influenza A (H5N1) among poultry. In Vietnam and Thailand, these outbreaks were associated with severe illnesses and deaths among humans. In the United States, the 2003-04 influenza season began earlier than most seasons, peaked in December, was moderately severe in terms of its impact on mortality, and was associated predominantly with influenza A (H3N2) viruses. This report 1) summarizes information collected by World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories, state and local health departments, health-care providers, vital statistics registries, and CDC and 2) describes influenza activity in the United States and worldwide during the 2003-04 influenza season and the composition of the 2004-05 influenza vaccine.     

Inactivated influenza vaccine effectiveness in children under 6 years of age during the 2002-2003 season

This study was carried out to investigate the effectiveness of influenza vaccine among 2913 children (1512 vaccinees and 1401 nonvaccinees) under 6 years of age during the 2002-2003 season. Study subjects were recruited from 54 paediatric clinics, located in eight areas in Japan. Maximum body temperatures were obtained weekly from parents between 2002 December 16 and 2003 April 13. Influenza-like illness (ILI) was defined as an acute febrile illness (> or =38.0 degrees C) during the peak epidemic period in each study area. The vaccine antigens included were A/New Caledonia/20/99(H1N1), A/Panama/2007/99(H3N2) and B/Shandong/7/97. Vaccine effectiveness was analyzed by comparing the frequencies of ILI between vaccinees and nonvaccinees. The adjusted odds ratio (OR) and its 95% confidence interval (95% CI) were calculated by the proportional odds model using logistic regression with three-level outcome variables (<38.0/38.0-38.9/> or =39.0 degrees C). A significantly decreased OR of vaccination was observed (OR: 0.76; 95% CI: 0.66-0.88), corresponding to a vaccine effectiveness (1-OR) of 24% (95% CI: 12%-34%). When the analysis was confined to those aged > or =2 years, a more pronounced OR (0.67, 0.56-0.79) was obtained with a vaccine effectiveness of 33% (21%-44%). On the other hand, no significant vaccine effectiveness was detected among very young children; the ORs were 1.84 (0.81-4.19) for those <1 year of age and 0.99 (0.72-1.36) for those 1.0-1.9 years of age and 1.07 (0.80-1.44) when these two age groups were combined. Thus, among very young children vaccine effectiveness could not be demonstrated.     

Annual report of the National Influenza Surveillance Scheme, 2003.

Surveillance of influenza in Australia is based on laboratory isolation of influenza viruses, sentinel general-practitioner practices for influenza-like illness, and absenteeism data from a major national employer. In 2003, the peak in influenza activity was in August which was later than in 2002. In 2003, 3,604 laboratory-confirmed cases of influenza were notified to the National Notifiable Diseases Surveillance System, which was marginally lower than for the previous year. Ninety-four per cent of the circulating viruses were influenza A. This was the highest proportion in the last five years. Nine hundred and thirty-five isolates were antigenically analysed: 928 were A(H3), two were A(H1) strains and five were influenza B viruses. The majority (98%) of the A(H3) subtypes were A/Fujian/411/2002(H3N2)-like and have shown a significant antigenic drift. The 2003 Australian influenza vaccine contained A/Panama/2007/99, which induced 2-4-fold lower antibody response against the drifted strain. An A/Fujian/411/2002(H3N2)-like virus has been incorporated in the Australian influenza vaccine for 2004. In 2003, the influenza vaccine was given to 77 per cent of Australians aged over 65 years; the same up take as in 2002.     

Interim within-season estimate of the effectiveness of trivalent inactivated influenza vaccine--Marshfield, Wisconsin, 2007-08 influenza season

During clinical trials, the efficacy of vaccination with inactivated influenza vaccines for the prevention of serologically confirmed influenza infection has been estimated as high as 70%-90% among healthier adults. However, the effectiveness of annual influenza vaccination typically is lower during those influenza seasons when a suboptimal match between the vaccine strains and circulating influenza strains is observed. For example, in a 4-year randomized study of influenza vaccine among healthy persons aged 1-65 years, the predominant strain was drifted from the vaccine strain in 2 of the 4 years. Inactivated vaccine effectiveness (VE) against culture-confirmed influenza ranged from 71% to 79% when the vaccine and circulating strains were suboptimally matched to 74% to 79% when the matches were well matched. In contrast, a 2-year study of inactivated influenza vaccine among healthy adults aged 18-64 years found no measurable VE during a year when a poorly matched strain circulated, but found VE of 86% against laboratory-confirmed influenza during the following year when the vaccine and circulating strains were well matched. Although laboratory data on the antigenic characteristics of circulating influenza viruses compared with vaccine strains are available during influenza seasons, estimates of VE usually have not been made until months after the conclusion of the season. This report summarizes interim results of a 2008 case-control study to estimate the effectiveness of trivalent inactivated influenza vaccine for prevention of medically attended, laboratory-confirmed influenza during the 2007-08 influenza season, when most circulating influenza A (H3N2) and B viruses were suboptimally matched to the vaccine strains. Despite the suboptimal match between two of three vaccine strains and circulating influenza strains, overall VE in the study population during January 21-February 8, 2008, was 44%. These findings demonstrate that, in any season, assessment of the clinical effectiveness of influenza vaccines cannot be determined solely by laboratory evaluation of the degree of antigenic match between vaccine and circulation strains.     

2003年广东省流感病毒的流行概况及特征

目的了解2003年广东省流感病毒的流行特点和抗原变异情况。方法根据广东地区流感监测资料进行分析；用交叉血凝抑制试验检测病毒的抗原性；用逆转录-聚合酶链反应扩增病毒HA1基因，纯化产物进行核苷酸序列测定。将序列和Genebank中相关序列进行比较，用MegAlign软件绘制种系发生树。结果全年分离到510株流感病毒，其中H3N2亚型流感481株，占92．4％；乙型流感29株，占7．6％。实验室证实流感爆发52起，其中50起暴发是由H3N2亚型流感病毒引起，2起暴发是由乙型流感病毒引起。H3N2亚型流感病毒抗原性和疫苗侏A／Panama／2007／99（H3N2）有所不同。类似干A／Fujian／411／02（H3N2）。在HAl区氨基酸序列上，和疫苗株A／Panama／2007／99（H3N2）同源性为92．1％，存在有25个氨基酸差异。28株乙型流感病毒属于Victoria系，抗原性类似疫苗侏B／HongKong／330／01，1株乙型病毒属于Yamagata系，抗原性不同干B／sichuan／379／99。结论2003年广东省流感活动比2002年要强；同时流行着甲型（H3N2）和2个谱系的乙型流感病毒，H3N2亚型毒侏是优势侏，抗原性发生了漂移。     

Effectiveness of triennial anti-influenza vaccination in French military during the 2003-2004 influenza season

BACKGROUND: Influenza may rapidly disseminate within populations living in confined settings, causing considerable morbidity and disrupting daily activities. The French military health-care system set up since 1994 a prevention strategy based on triennial anti-influenza vaccination. The aim of this study was to evaluate the effectiveness of this strategy during the 2003-2004 influenza season. METHODS: We conducted a matched case-control study from 10/01/2003 through 3/31/2004. Cases were laboratory-confirmed influenza cases. The controls were not to have presented influenza during all the period of study. Controls were matched to cases by sex, army unit and age. Subgroups were categorized into four groups by vaccination regimen [0-1 year], [1-2 years], [2-3 years], [3 years and more or unvaccinated]. RESULTS: One hundred and eighteen cases and 435 controls were included. The proportion of correctly vaccinated subjects (相似文献   

The 2002/2003 influenza season in the Netherlands and the vaccine composition for the 2003/2004 season

As in the 2000/2001 and 2001/2002 seasons, the influenza epidemic in the 2002/2003 season started late (week 7 of 2003) and was only moderate in size. Influenza A (H3N2) and B viruses were detected in equal numbers among patients of general practitioners and these two viruses were therefore equally responsible for the epidemic. However, H3N2 viruses dominated isolates taken from hospitals. In haemagglutination-inhibition (HI) assays most of the H3N2 viruses proved highly reactive with antiserum to the vaccine-reference strain A/Moscow/10/99. This was also true for a number of isolates, including those obtained from nursing home residents, closely related to the reference strain A/Finland/170/03. However, an estimated 4% of the H3N2 isolates belonged to the variant A/Fujian/411/02 from China, which constituted the majority of the H3N2 viruses isolated in Europe in the later phase of the season. This variant reacted poorly with antiserum to A/Moscow/10/99. In H1 tests all influenza A(H1N1)-virus isolates and all B-virus isolates were closelyrelated to the corresponding vaccine-reference strains. Taking this data into consideration, the World Health Organization has advised the same vaccine composition for the 2003/2004 season as for the 2002/2003 season, namely: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Hong Kong/330/01. There is the possibility of a mismatch occurring between the H3N2-vaccine strain and the circulating H3N2 viruses in the coming influenza season. In March and April 2003 there was an outbreak of influenza-A (H7N7) fowl plague in the Netherlands. A special monitoring survey revealed that 91 people who had handled infected poultry became infected with the H7N7 virus. One of these later died as a result of this. None of the avian and human H7N7-virus isolates examined contained human or porcine influenza-A virus genes.     

Update: influenza activity--United States and worldwide, 2002-03 season,and composition of the 2003-04 influenza vaccine

In collaboration with the World Health Organization (WHO), its collaborating laboratories, state and local health departments, health-care providers, and vital statistic registries, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. During the 2002-03 influenza season, influenza A (H1), A (H3N2), and B viruses co-circulated in the Northern Hemisphere. Human infections with avian influenza A (H5N1) and A (H7N7) viruses were reported in Hong Kong and the Netherlands, respectively. In the United States, the 2002-03 influenza season was mild; influenza A (H1) and B viruses circulated widely, and the predominant virus varied by region and time of season. This report summarizes influenza activity in the United States and worldwide during the 2002-03 influenza season and describes the composition of the 2003-04 influenza vaccine.     

Cross-reactivity of influenza A (H3N2) hemagglutination-inhibition antibodies induced by an inactivated influenza vaccine

The antigenic drift of influenza A (H3N2) virus in 2003-2004 necessitated a change in the vaccine from the A/Panama to the A/Wyoming strain for the 2004-2005 season. Using hemagglutination inhibition, we therefore tested antibodies in sera of 39 individuals (mean age 64.6 years) at the end of the 2003-2004 season for cross-reactivity to vaccine strains and H3N2 antigens subject to antigenic drift. Antibodies against both A (H3N2) Panama and Wyoming developed in 5/13 (38.5%) unvaccinated individuals, whereas, 22/26 (84.6%) vaccinees developed antibodies to Panama and 21/26 (80.8%) to Wyoming. None of these individuals suffered an influenza episode that season. The results suggest that the elderly might develop protective levels of cross-reactive A (H3N2) Wyoming HI antibodies following vaccination with the Panama strain. Such strains, like the ones included in the 2003-2004 influenza vaccine, might be expected to provide a broad-spectrum antibody response that could be effective even in the face of single season antigenic drift.     

Comparing influenza vaccine effectiveness between cell-derived and egg-derived vaccines, 2017–2018 influenza season

The Department of Defense Global Respiratory Pathogen Surveillance Program conducted a study to compare the differences in vaccine effectiveness (VE) of the cell-derived and egg-derived vaccines. DoD healthcare beneficiaries, excluding service members, that presented with influenza-like illness for the period of 1 October 2017 through 28 April 2018 were included in a test-negative case-control study examining laboratory confirmed influenza infections. Three VE analyses were performed (1) influenza infection among those vaccinated with cell-derived vaccines (2) influenza infection among those vaccinated with egg-derived vaccines and a (3) relative VE which directly compared the odds of influenza infection with cell-derived vaccine against those with egg-derived vaccines. The cell-derived and egg-derived vaccines were moderately protective against all influenza types with significant VE estimates for all dependents at 46% (95% confidence interval, 33, 56) and 53% (45, 60), respectively. Of the subtype analyses, influenza A(H1N1)pdm09 performed the best. In the cell-derived vaccine, the adult age group was moderate to high at 71% (44, 85) and children moderate at 56% (15, 75). In the egg-derived vaccine, the children age group was at a high 88% (80, 93) effectiveness and adults at 81% (56, 92). When comparing cell-derived vaccine directly to the egg-derived vaccine, the relative VE found significant results only for influenza A(H1N1)pdm09 which favored the egg-derived vaccine with odds ratios of 2.0 (1.1, 3.6) for all dependents and 2.9 (1.3, 6.3) for children. In the influenza A(H3N2) analysis, statistical significance was not gained; however, the odds favored the cell-derived vaccine.     

新疆地区2003-2004年麻疹野病毒分离株基因特征分析

目的了解新疆地区流行的麻疹野病毒基因型和亚型特征。方法对2003-2004年用健康产婴儿脐带血单个核细胞分离的麻疹野病毒进行分子流行病学分析。采用逆转录-聚合酶链反应对麻疹病毒N基因C末端676个核苷酸片段进行扩增，并对扩增产物进行核苷酸序列测定。通过分析C末端450个核苷酸序列构建基因亲缘关系树，并分析毒株变异情况。结果2003年和2004年各分离麻疹病毒3株（XJ03-26、XJ03-27、XJ03-74、XJ04-146、XJ04-150、XJ04-152），除XJ03-26株与沪191株核苷酸差异〈1％，属疫苗相关株A基因型外，其余5株均为H1基因型。其中XJ03-27、XJ03-74、XJ04-150和XJ04-152与H1a参考株China9322的核苷酸差异为0．5％～1．6％，同属于H1a亚型；XJ04-146与H1b参考株China9475的核苷酸同源性为98．7％，属于H1b亚型。4株H1a毒株分属两组（即XJ03-27与XJ04-150，XJ03-74与XJ04-152），每组内毒株N基因碳末端450个核苷酸序列几近相同无差异，但两组间毒株却存在较大变异，核苷酸差异达6．1％（27个核苷酸差异）。结论新疆地区2003-2004年流行的麻疹病毒以H1a亚型为主，亦存在H1b亚型。     

Intanza(®) 15 mcg intradermal influenza vaccine elicits cross-reactive antibody responses against heterologous A(H3N2) influenza viruses

The aim of the present study was to explore the ability of Intanza^® 15 μg, the intradermal (ID) trivalent inactivated split-virion influenza vaccine containing 15 μg hemagglutinin per strain, to enhance the antibody responses against heterologous circulating H3N2 strains in adults 60 years and older. During the 2006–2007 influenza season, subjects aged 60 years or older were randomly assigned to receive one dose of ID or an intramuscular (IM, Vaxigrip^®) influenza vaccine, which contained the reassortant A/Wisconsin/67/05(H3N2) strain as the H3N2 component. Antibody responses were assessed against the homologous vaccine strain, against the A/Brisbane/10/07(H3N2) reassortant strain and against four heterologous H3N2 field isolates (A/Genoa/62/05(H3N2), A/Genoa/3/07(H3N2), A/Genoa/2/07(H3N2), A/Genoa/3/06(H3N2)). The viruses tested belonged to three different clades that were closely related antigenically to A/California/7/04(H3N2), A/Nepal/921/06(H3N2) and A/Brisbane/10/07(H3N2). Antibody responses to these viruses were measured in 25 subjects per group using both haemagglutination inhibition (HI) and neutralization (NT) assays.     

The 2001/2002 influenza season and the vaccine composition for the 2002/2003 season

The epidemic in the influenza season 2001/2002 was of moderate activity just like in 2000/2001. The influenza epidemic started in week 2 of 2002 when the clinical influenza activity reported by the general practitioner network of the Netherlands Institute of Primary Health Care (NIVEL) increased. This was caused by influenza A viruses of the H3N2 subtype in particular. All influenza A viruses of this subtype were closely related to the vaccine strain for this subtype, A/Moscow/10/99. Influenza B viruses and influenza A/H1 viruses isolated this season had surprising features. The influenza B viruses originated from two lineages. Viruses of the B/Yamagata/16/88 lineage have been circulating for more than twelve years. The vaccine reference strain B/Sichuan/379/99 belongs to this lineage. The B/Victoria/2/87 lineage reappeared again after an absence in Europe of more than ten years and accounted for 50% of the influenza B viruses that were isolated in the Netherlands. Therefore the vaccine will have provided only partial protection against influenza B. The only influenza A/H1 virus that was isolated appeared to be of a new subtype H1N2. The H1 hemagglutinin of this virus was closely related to that of the vaccine strain A/New Caledonia/20/99. The N2 neuraminidase originated from recent human influenza A/H3N2 viruses. Therefore the vaccine probably provided good protection against the new H1N2 subtype. Based in part on these data, the World Health Organization has advised that the vaccines for the season 2002/2003 should contain the following or comparable influenza-virus strains: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Hong Kong/330/01, the latter being an influenza B virus of the B/Victoria/2/87 lineage.     

新疆维吾尔自治区2003～2004年麻疹野病毒分离株基因特征分析

目的了解新疆维吾尔自治区流行的麻疹野病毒的基因型或亚型特征,为消除麻疹提供科学依据。方法对2003~2004年用健康产婴脐血单个核细胞分离的麻疹野病毒进行分子流行病学分析。采用逆转录-聚合酶链反应对麻疹病毒核蛋白(N)基因羧基(COOH)末端676个核苷酸片段进行扩增,并测定扩增产物的核苷酸序列。通过分析COOH末端450个核苷酸序列构建基因亲缘关系树,并分析毒株变异情况。结果2003年和2004年各分离麻疹病毒3株(XJ03-26、XJ03-27、XJ03-74;XJ04-146、XJ04-150、XJ04-152),除XJ03-26株与沪191株核苷酸差异<1%,属疫苗相关株A基因型外,其余5株均为H1基因型。其中XJ03-27、XJ03-74、XJ04-150、XJ04-152与H1a参考株China9322的核苷酸差异为0.5%~1.6%,同属于H1a亚型;XJ04-146与H1b参考株China9475的核苷酸同源性为98.7%,属于H1b亚型。4株H1a毒株分属两组(即XJ03-27与XJ04-150,XJ03-74与XJ04-152),每组内毒株N基因COOH末端450个核苷酸序列几近相同或无差异。结论新疆维吾尔自治区2003~2004年流行的麻疹病毒以H1a亚型为主,亦存在H1b亚型。新疆维吾尔自治区流行的麻疹野病毒间存在较大基因变异,不同年份存在相同麻疹病毒的持续循环传播,需加强麻疹疫苗的预防接种及病毒学监测。     

Influenza in Poland in 2003

Following two years of low influenza incidence in Poland, the activity of this disease markedly increased in 2003. In total 1,216,285 cases of influenza like illness were registered (incidence 3,184.4 per 100,000). Regionally the incidence ranged from 1,195.7 in Zachodniopomorskie to 5,719.7 per 100,000 in Mazowieckie. Children and adolescents under 15 years of age accounted for 41.7% of all cases (507,102 cases, age specific incidence 7,579.0 per 100,000). In this age group the incidence varied regionally from 2,718.1 in Podlaskie to 14,087.6 per 100,000 in Mazowieckie. 3,128 patients (0.26% of all cases) required hospital admission. There were 141 deaths due to influenza (mortality 0.12%) in 2003, in 78.7% these were persons over 70 years of age. Nineteen strains of influenza virus were isolated in 2003 in Poland, including 15 strains of subtype A(H3), 3 strains of subtype A(H1) and one strain of type B. Besides, in other 10 cases influenza A infection was confirmed by direct immunofluorescence test. All isolated influenza strains were antigenically similar to the vaccine strains recommended for the epidemic season 2002/03 and 2003/04.     

Antibodies cross-reactive to influenza A (H3N2) variant virus and impact of 2010-11 seasonal influenza vaccine on cross-reactive antibodies - United States

Since August 2011, a total of 12 human infections with influenza A (H3N2) variant viruses with genes from avian, swine, and human viruses (i.e., A [H3N2]v) that had acquired the M gene from influenza A (H1N1)pdm09 virus have been reported to CDC. Eleven of the cases occurred in children aged <10 years. In six cases, no history of recent exposure to swine was noted, suggesting that human-to-human transmission had occurred. This new gene constellation for A (H3N2)v viruses and its temporal association with an increase in human cases of A (H3N2)v highlight the need to better understand the risk for human infection with these viruses and the extent to which current seasonal vaccines might elicit cross-reactive antibodies to them. CDC conducted a preliminary analysis to evaluate the age-specific presence of serum cross-reactive antibody in U.S. populations vaccinated or not vaccinated with the 2010-11 seasonal trivalent influenza vaccine (TIV). The results indicated that 1) little or no cross-reactive antibody to A (H3N2)v exists among children aged <10 years, 2) immunization with the 2010-11 TIV had no impact on cross-reactive antibody levels in those aged <3 years, 3) cross-reactive antibody was detected in 20%-30% of those aged ≥10 years, and 4) among adults, vaccination with TIV provided a modest boost to the level of cross-reactive A (H3N2)v antibodies. Receipt of seasonal influenza vaccine continues to be recommended to protect against circulating human influenza viruses for all age groups and might provide limited protection against A (H3N2)v infection in the adult population. A vaccine virus specific for A (H3N2)v has been developed and could be used to produce an H3N2v vaccine, if needed.     

Long term effectiveness of adjuvanted influenza A(H1N1)pdm09 vaccine in children

BackgroundImmunological studies have indicated that the effectiveness of AS03 adjuvanted monovalent influenza A(H1N1)pdm09 vaccine (Pandemrix^®) may be of longer duration than what is seen for non-adjuvanted seasonal influenza vaccines. Sixty-nine percent of children 6 months–18 years of age in Stockholm County received at least one dose of Pandemrix^® during the 2009 pandemic. We studied the effectiveness of the vaccine during the influenza seasons 2010–2011 and 2012–2013 in children hospitalized with virologically confirmed influenza. The season 2011–2012 was not included, since influenza A(H3N2) was the predominant circulating strain.MethodsIn a retrospective case-control study using a modified test-negative design we compared the percentage vaccinated with Pandemrix^® among children diagnosed with influenza A(H1N1)pdm09 (cases), with that of those diagnosed with influenza A(H3N2) or influenza B (controls) during the two seasons. We excluded children born after July 1, 2009, since only children who were 6 months of age or older received the pandemic vaccine in October–December 2009.ResultsDuring the 2010–2011 season, 3/16 (19%) of children diagnosed with influenza A(H1N1)pdm09, vs. 32/41 (78%) of those with influenza A(H3N2) or influenza B had been vaccinated with Pandemrix^® in 2009. The odds ratio, after adjustment for sex, age and underlying diseases, for becoming a case when vaccinated with Pandemrix^® was 0.083 (95%CI 0.014, 0.36), corresponding to a VE of 91.7%. During the season 2012–2013, there was no difference between the two groups; 59% of children diagnosed with influenza A(H3N2)/B and 60% of those with influenza A(H1N1)pdm09 had been vaccinated with Pandemrix^® in 2009.ConclusionThe AS03 adjuvanted monovalent influenza A(H1N1) pdm09 vaccine (Pandemrix^®) was effective in preventing hospital admission for influenza A(H1N1)pdm09 in children during at least two seasons.     

The 2003/2004 influenza season in the Netherlands with a limited epidemic of the virus variant A/Fujian, and the vaccine composition for the 2004/2005 season

In contrast to the three previous influenza seasons, the influenza epidemic of the 2003/2004 season started early in week 49 of 2003. The epidemic was predominantly caused by influenza-A viruses of the H3N2 subtype. All isolated influenza-A viruses were antigenically related to influenza virus A/Fujian/411/02, which was already detected in the influenza season 2002/2003 and that deviated from the vaccine-reference strain A/Moscow/10/99 to a certain extent. The magnitude of the epidemic was limited despite the fact that it was caused by influenza-A H3N2-virus-drift variants. Immunity caused by natural infection with influenza viruses during previous seasons or vaccination has possibly provided sufficient cross protection against these new H3N2-drift variant. No influenza-A viruses of the H1N1 or H1N2 subtypes were detected in the influenza season 2003/2004. Only a small number of influenza-B viruses were isolated, which all belonged to the B/Yamagata/16/88 lineage, which was temporarily replaced by the B/Victoria2/87 lineage in the previous influenza season. On the basis of epidemiological and serological data the World Health Organization has recommended the following vaccine composition for the 2004/2005 influenza season: A/Fujian/411/02 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Shanghai/361/02.