The US 2010-2011 influenza vaccines were moderately effective in preventing medically attended influenza during a season when all 3 vaccine strains were antigenically similar to circulating viruses. Continued monitoring of influenza vaccines in all age groups is important, particularly as new vaccines are introduced.

Human herpesvirus 6 congenital infection results primarily from chromosomally integrated virus which is passed through the germ-line. Infants with chromosomally integrated human herpesvirus 6 had high viral loads in all specimens, produced human herpesvirus 6 antibody, and mRNA. The clinical relevance needs study as 1 of 116 newborns may have chromosomally integrated human herpesvirus 6 blood specimens.

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We estimated the effectiveness of four monovalent pandemic influenza A (H1N1) vaccines (three unadjuvanted inactivated, one live attenuated) available in the U.S. during the pandemic. Patients with acute respiratory illness presenting to inpatient and outpatient facilities affiliated with four collaborating institutions were prospectively recruited, consented, and tested for influenza. Analyses were restricted to October 2009 through April 2010, when pandemic vaccine was available. Patients testing positive for pandemic influenza by real-time RT-PCR were cases; those testing negative were controls. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, patient age, timing of illness, insurance status, enrollment site, and presence of high-risk medical conditions. Pandemic virus was detected in 1,011 (15%) of 6,757 enrolled patients. Fifteen (1%) of 1,011 influenza positive cases and 1,042 (18%) of 5,746 test-negative controls had record-verified pandemic vaccination >14 days prior to illness onset. Adjusted effectiveness (95% confidence interval) for pandemic vaccines combined was 56% (23%, 75%). Adjusted effectiveness for inactivated vaccines alone (79% of total) was 62% (25%, 81%) overall and 32% (−92%, 76%), 89% (15%, 99%), and −6% (−231%, 66%) in those aged 0.5 to 9, 10 to 49, and 50+ years, respectively. Effectiveness for the live attenuated vaccine in those aged 2 to 49 years was only demonstrated if vaccination >7 rather than >14 days prior to illness onset was considered (61%∶ 12%, 82%). Inactivated non-adjuvanted pandemic vaccines offered significant protection against confirmed pandemic influenza-associated medical care visits in young adults.

Objectives The goal was to estimate the effectiveness of influenza vaccination against laboratory-confirmed influenza during the 2003–2004 and 2004–2005 influenza seasons in children aged 6-59 months. Methods We conducted a case-control study in children with a medically attended acute respiratory infection who received care in the inpatient, emergency department or outpatient clinic setting during two consecutive influenza seasons. All children resided in Monroe County, NY, Davidson County, TN or Hamilton County, OH, were prospectively enrolled at the time of acute illness, and had nasal/throat swabs tested for influenza by culture and/or polymerase chain reaction. Children with laboratory-confirmed influenza were cases and children who tested negative for influenza were controls. Child vaccination records from the parent and from the child's physician were used to determine and validate influenza vaccination status. Influenza vaccine effectiveness was calculated as (1 – adjusted odds ratio) × 100. Results We enrolled 288 cases and 744 controls during the 2003–2004 season, and 197 cases and 1,305 controls during the 2004–2005 season. Six percent and 19% of all study children were fully vaccinated according to immunization guidelines in the respective seasons. Full vaccination was associated with significantly fewer influenza-related inpatient, emergency department, or outpatient clinic visits in 2004-2005 [vaccine effectiveness = 57% (95% CI: 28%-74%)], but not in 2003-2004 [vaccine effectiveness = 44% (95% CI: -42%-78%)]. Partial vaccination was not effective in either season. Conclusions Receipt of all recommended doses of influenza vaccine was associated with halving of laboratory-confirmed influenza-related medical visits among children aged 6-59 months in one of two study years, despite suboptimal matches between the vaccine and circulating influenza strains in both years.