Effectiveness of seasonal influenza vaccines in the United States during a season with circulation of all three vaccine strains.

BACKGROUND: Influenza vaccines may be reformulated annually because of antigenic drift in influenza viruses. However, the relationship between antigenic characteristics of circulating viruses and vaccine effectiveness (VE) is not well understood. We conducted an assessment of the effectiveness of US influenza vaccines during the 2010-2011 season. METHODS: We performed a case-control study comparing vaccination histories between subjects with acute respiratory illness with positive real-time reverse transcription polymerase chain reaction for influenza and influenza test-negative controls. Subjects with acute respiratory illness of ≤7 days duration were enrolled in hospitals, emergency departments, or outpatient clinics in communities in 4 states. History of immunization with the 2010-2011 vaccine was ascertained from vaccine registries or medical records. Vaccine effectiveness was estimated in logistic regression models adjusted for study community, age, race, insurance status, enrollment site, and presence of a high-risk medical condition. RESULTS: A total of 1040 influenza-positive cases and 3717 influenza-negative controls were included from the influenza season, including 373 cases of influenza A(H1N1), 334 cases of influenza A(H3N2), and 333 cases of influenza B. Overall adjusted VE was 60% (95% confidence interval [CI], 53%-66%). Age-specific VE estimates ranged from 69% (95% CI, 56%-77%) in children aged 6 months-8 years to 38% (95% CI, -16% to 67%) in adults aged ≥65 years. CONCLUSIONS: 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.

Transplacental congenital human herpesvirus 6 infection caused by maternal chromosomally integrated virus.

Congenital human herpesvirus 6 (HHV-6) infection results from germline passage of chromosomally integrated HHV-6 (CI-HHV-6) and from transplacental passage of maternal HHV-6 infection. We aimed to determine whether CI-HHV-6 could replicate and cause transplacentally acquired HHV-6 infection. HHV-6 DNA, variant type, and viral loads were determined with samples (cord blood, peripheral blood, saliva, urine, and hair) obtained from 6 infants with transplacentally acquired HHV-6 and with samples of their parents' hair. No fathers but all mothers of infants with transplacentally acquired HHV-6 had CI-HHV-6, and the mother's CI-HHV-6 variant was the same variant causing the transplacentally acquired congenital HHV-6 infection. This suggests the possibility that CI-HHV-6 replicates and may cause most, if not all, congenital HHV-6 infections.

Diagnostic assays for active infection with human herpesvirus 6 (HHV-6).

BACKGROUND: Human herpesvirus 6 (HHV-6) causes ubiquitous infection in early childhood with lifelong latency or persistence. Reactivation of HHV-6 has been associated with multiple diseases including encephalitis. Chromosomal integration of HHV-6 also occurs. Previous studies have suggested that the detection of HHV-6 DNA in plasma is an accurate marker of active viral replication. OBJECTIVE: We sought to determine whether PCR assays on plasma could correctly differentiate between primary HHV-6 infection, chromosomal integration of HHV-6 and latent HHV-6 infection. STUDY DESIGN: We performed qualitative PCR, real-time quantitative PCR (RQ-PCR), and reverse-transcriptase PCR (RT-PCR) assays on samples of peripheral and cord blood mononuclear cells, as well as plasma, from groups of subjects with well defined HHV-6 infection, including subjects with chromosomally integrated HHV-6. RESULTS AND CONCLUSIONS: The detection of HHV-6 DNA in plasma was 92% sensitive compared to viral isolation for the identification of primary infection with HHV-6. All plasma samples from infants with chromosomally integrated HHV-6 had HHV-6 DNA detectable in plasma while only 5.6% were positive by RT-PCR. The specificity of plasma PCR for active replication of HHV-6 was 84% compared to viral culture while the specificity of RT-PCR was 98%. Our results demonstrate that qualitative or quantitative PCR of plasma is insufficient to distinguish between active viral replication and chromosomal integration with HHV-6. We found a higher specificity of RT-PCR performed on PBMC samples compared to PCR or RQ-PCR performed on plasma when evaluating samples for active HHV-6 replication.

Chromosomal integration of human herpesvirus 6 is the major mode of congenital human herpesvirus 6 infection.

OBJECTIVE: We examined the frequency and characteristics of chromosomally integrated human herpesvirus 6 among congenitally infected children. METHODS: Infants with and without congenital human herpesvirus 6 infection were prospectively monitored. Cord blood mononuclear cell, peripheral blood mononuclear cell, saliva, urine, and hair follicle samples were examined for human herpesvirus 6 DNA. Human herpesvirus 6 RNA, serum antibody, and chromosomally integrated human herpesvirus 6 levels were also assessed. RESULTS: Among 85 infants, 43 had congenital infections and 42 had postnatal infections. Most congenital infections (86%) resulted from chromosomally integrated human herpesvirus 6; 6 infants (14%) had transplacental infections. Children with chromosomally integrated human herpesvirus 6 had high viral loads in all sites (mean: 5-6 log(10) genomic copies per mug of cellular DNA); among children with transplacental infection or postnatal infection, human herpesvirus 6 DNA was absent in hair samples and inconsistent in other samples, and viral loads were significantly lower. One parent of each child with chromosomally integrated human herpesvirus 6 who had parental hair samples tested had hair containing human herpesvirus 6 DNA. Variant A caused 32% of chromosomally integrated human herpesvirus 6 infections, compared with 2% of postnatal infections. Replicating human herpesvirus 6 was detected only among chromosomally integrated human herpesvirus 6 samples (8% of cord blood mononuclear cells and peripheral blood mononuclear cells). Cord blood human herpesvirus 6 antibody levels were similar among children with chromosomally integrated human herpesvirus 6, transplacental infection, and postnatal infection and between children with maternal and paternal chromosomally integrated human herpesvirus 6 transmission. CONCLUSIONS: 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.

Vaccine effectiveness against laboratory-confirmed influenza in children 6 to 59 months of age during the 2003-2004 and 2004-2005 influenza seasons.

OBJECTIVE: 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 6 to 59 months of age. METHODS: We conducted a case-control study with children with medically attended, acute respiratory infections who received care in an inpatient, emergency department, or outpatient clinic setting during 2 consecutive influenza seasons. All children residing in Monroe County, New York, Davidson County, Tennessee, or Hamilton County, Ohio, were enrolled prospectively at the time of acute illness and had nasal/throat swabs tested for influenza with cultures and/or polymerase chain reaction assays. Children with laboratory-confirmed influenza were case subjects and children who tested negative for influenza were control subjects. Child vaccination records from the parent and the child's physician were used to determine and to validate influenza vaccination status. Influenza vaccine effectiveness was calculated as (1 - adjusted odds ratio) x 100. RESULTS: We enrolled 288 case subjects and 744 control subjects during the 2003-2004 season and 197 case subjects and 1305 control subjects 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%) but not in 2003-2004 (vaccine effectiveness: 44%). 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 6 to 59 months of age in 1 of 2 study years, despite suboptimal matches between the vaccine and circulating influenza strains in both years.

Influenza vaccine effectiveness among children 6 to 59 months of age during 2 influenza seasons: a case-cohort study.

OBJECTIVE: To measure vaccine effectiveness (VE) in preventing influenza-related health care visits among children aged 6 to 59 months during 2 consecutive influenza seasons. DESIGN: Case-cohort study estimating effectiveness of inactivated influenza vaccine in preventing inpatient/outpatient visits (emergency department [ED] and outpatient clinic). We compared vaccination status of laboratory-confirmed influenza cases with a cluster sample of children from a random sample of practices in 3 counties (subcohort) during the 2003-2004 and 2004-2005 seasons. SETTING: Counties encompassing Rochester, New York, Nashville, Tennessee, and Cincinnati, Ohio. PARTICIPANTS: Children aged 6 to 59 months seen in inpatient/ED or outpatient clinic settings for acute respiratory illnesses and community-based subcohort comparison. Main Exposure Influenza vaccination. MAIN OUTCOME MEASURES: Influenza vaccination status of cases vs subcohort using time-dependent Cox proportional hazards models to estimate VE in preventing inpatient/ED and outpatient visits. RESULTS: During the 2003-2004 and 2004-2005 seasons, 165 and 80 inpatient/ED and 74 and 95 outpatient influenza cases were enrolled, while more than 4500 inpatient/ED and more than 600 outpatient subcohorts were evaluated, respectively. In bivariate analyses, cases had lower vaccination rates than subcohorts. However, significant influenza VE could not be demonstrated for any season, age, or setting after adjusting for county, sex, insurance, chronic conditions recommended for influenza vaccination, and timing of influenza vaccination (VE estimates ranged from 7%-52% across settings and seasons for fully vaccinated 6- to 59-month-olds). CONCLUSION: In 2 seasons with suboptimal antigenic match between vaccines and circulating strains, we could not demonstrate VE in preventing influenza-related inpatient/ED or outpatient visits in children younger than 5 years. Further study is needed during years with good vaccine match.

Human herpesvirus (HHV)-6 and HHV-7 infections in pregnant women.

BACKGROUND: Both intrauterine and sexual transmission of human herpesvirus (HHV)-6 and HHV-7 have been suggested, and congenital HHV-6 infection does occur. We prospectively studied HHV-6 and HHV-7 at multiple sites in pregnant women to determine the characteristics of these viruses at repeated time points. METHODS: Peripheral blood mononuclear cells (PBMCs), cervical secretions, placenta, and cord blood were tested by nested polymerase chain reaction (PCR) and reverse-transcriptase PCR for HHV-6 and HHV-7 and by quantitative PCR for HHV-6. A control group of women was also studied. RESULTS: We enrolled 104 pregnant and 31 control women. HHV-7 DNA was detected more frequently in PBMCs from pregnant women (66.9%) than HHV-6 DNA (22.2%; P<.0001), but both were found at low rates in cervical swabs (HHV-7 vs. HHV-6 DNA, 3.0% vs. 7.5%; P=.19). Pregnant women with HHV-6 DNA present in cervical swabs had a greater odds of having HHV-6 DNA present in the blood than did pregnant women with negative cervical swabs (odds ratio, 12.9; P=.0009). HHV-6 reactivation or reinfection was suggested in 17% of pregnant women. One placental sample had active HHV-6 replication. CONCLUSIONS: Detection of HHV-6 DNA in cervical secretions is associated with HHV-6 DNA in PBMC samples. Active placental infection along with congenital HHV-6 infection was identified.

Characteristics and acquisition of human herpesvirus (HHV) 7 infections in relation to infection with HHV-6.

Although both human herpesvirus (HHV) 6 and HHV-7 infections are ubiquitous during childhood, few acute HHV-7 infections are identified. It is unknown whether HHV-7 viremia indicates primary infection, as with HHV-6, or reactivation, and if these differ clinically. We studied, in otherwise healthy children < or =10 years old, HHV-7 and HHV-6 infections and their interaction by serologic assessment, viral isolation, and polymerase chain reaction. In children < or =24 months of age, HHV-7 infections occurred less often than HHV-6 infections (P< or =.002). Of 2806 samples from 2365 children < or =10 years old, 30 (1%) showed evidence of HHV-7 viremia; 23 (77%) of these were primary and 7 (23%) were reactivated HHV-7 infections. Four (13%) showed concurrent HHV-6 viremia, 2 associated with primary HHV-7 infections. The clinical manifestations of primary and reactivated HHV-7 infections were similar, except that seizures occurred more frequently in reactivated infections. These findings, previously unrecognized in otherwise healthy children, suggest that HHV-7 viremia could represent primary or reactivated infection and may be affected by the interaction between HHV-6 and HHV-7.

Seven-year follow-up of vaccine response in extremely premature infants.

OBJECTIVE: To assess the immune response of 7-year-old former extremely preterm (PT) infants to routine childhood immunizations. METHODS: Sixteen PT (<29 weeks and <1000 g) infants, followed since their primary immunizations at the recommended chronological ages, and 16 age-matched full-term (FT) control subjects were evaluated at 7 years of age. Antibodies to Haemophilus influenzae type b polyribosylribitol phosphate (Hib-PRP), tetanus, pertussis, diphtheria, polio, and hepatitis B (HBsAb) were measured. RESULTS: The FT group had higher antidiphtheria geometric mean titers (GMT) than the PT group (1.07 vs 0.36 IU/mL). All FT and 13 of 16 PT had protective diphtheria antibody titers (>0.1 IU/mL). The tetanus GMT were 4.22 IU/mL (FT) and 1.99 IU/mL (PT). All children had protective tetanus titers (>0.01 IU/mL). Pertussis titers did not differ between FT and PT. Hib-PRP GMT were higher in FT than in PT (3.21 vs 1.41 microg/mL). All children had anti-PRP > or = 0.15 microg/mL; 12 of 16 FT and 10 of 16 PT had levels > or = 1.0 microg/mL. Polio serotype 1 and 2 GMT were similar between groups, and all children had protective titers (> or = 8). Polio serotype 3 GMT were 59 (FT) and 24 (PT) Karber units; all FT and 12 of 16 PT had protective titers. Among children who had received hepatitis B vaccine, GMT were similar in FT and PT children (120 vs 186 mIU/mL, and similar proportions of children (11 of 16 FT and 12 of 14 PT) had protective HBsAb titers (>10 mIU/mL). CONCLUSIONS: At 7 years of age, PT children had lower antibody titers to many vaccine antigens than FT children. However, most PT children maintained antibody titers in the protective range.

Congenital infections with human herpesvirus 6 (HHV6) and human herpesvirus 7 (HHV7).

OBJECTIVE: To examine whether: (1) congenital human herpesvirus 6 (HHV6) and human herpesvirus 7 (HHV7) infections occur; whether (2) their manifestations differ from postnatal infections; and whether (3) HHV6 and HHV7 infections differ despite their close relatedness. STUDY DESIGN: HHV6 and HHV7 infections acquired congenitally and postnatally in normal children were compared using viral isolation, serology, reverse-transcription polymerase chain reaction (RT-PCR) and nested DNA-PCR for HHV6 variant A (HHV6A), HHV6 variant B (HHV6B), and HHV7. RESULTS: HHV6 DNA was detected in 57 (1%) of 5638 cord bloods. HHV7 DNA, however, was not detected in 2129 cord bloods. Congenital HHV6 infections differed from postnatal infections, which were acute febrile illnesses. Congenital infections were asymptomatic, 10% demonstrated reactivation at birth, and HHV6 DNA persistence in follow-up blood samples was significantly more frequent. One-third of congenital infections were HHV6A, whereas all postnatal infections were HHV6B. CONCLUSIONS: Congenital HHV6 infections occurred in 1% of births, similar to the rate for cytomegalovirus infection. Congenital infections were clinically and virologically distinct from postnatal infections. Congenital HHV7 infections, however, were not detected, suggesting considerable differences in transmission and pathogenesis in these closely related beta-herpesviruses.

Human herpesvirus 6 (HHV6) DNA persistence and reactivation in healthy children.

OBJECTIVE: To determine in healthy children after primary infection the persistence of human herpesvirus 6 (HHV6) DNA, the presence and frequency of HHV6 re-activation or re-infection, and the relationship of both to illness and the presence of human herpesvirus 7 (HHV7) infection. STUDY DESIGN: Children 1 to 12 years of age with previous HHV6 infection were prospectively evaluated by HHV6 and HHV7 DNA polymerase chain reaction (PCR) and reverse transcription (RT)-PCR for HHV6. HHV6 plasma antibody titers were measured. Illnesses were recorded by diary, and physician records were reviewed. RESULTS: HHV6 DNA was detected in >or=1 peripheral blood mononuclear cell (PBMC) samples in 89% of children. HHV6 reactivation and re-infection were detected by RT-PCR in 1.1% of samples. Detection of HHV6 DNA was intermittent in 76% of children and was not associated with cumulative rates of illness. Illness at a study visit was significantly associated with the absence of HHV6 and HHV7 DNA in PBMC samples and was not associated with HHV6 antibody titer or the presence of HHV6 DNA in saliva. CONCLUSIONS: HHV6 DNA persists in most children intermittently following primary infection and is unrelated to illness. Reactivation of HHV6 occurs in healthy children without apparent illness.