STATEMENT ON SEASONAL INFLUENZA VACCINE FOR 2012-2013: An Advisory Committee Statement (ACS) National Advisory Committee on Immunization (NACI)

Resource utilization and cost of influenza requiring hospitalization in Canadian adults: A study from the serious outcomes surveillance network of the Canadian Immunization Research Network

BACKGROUND

Consideration of cost determinants is crucial to inform delivery of public vaccination programs.

OBJECTIVES

To estimate the average total cost of laboratory-confirmed influenza requiring hospitalization in Canadians prior to, during, and 30 days following discharge. To analyze effects of patient/disease characteristics, treatment, and regional differences in costs.

METHODS

Study utilized previously recorded clinical characteristics, resource use, and outcomes of laboratory-confirmed influenza patients admitted to hospitals in the Serious Outcomes Surveillance (SOS), Canadian Immunization Research Network (CIRN), from 2010/11 to 2012/13. Unit costs including hospital overheads were linked to inpatient/outpatient resource utilization before and after admissions.

RESULTS

Dataset included 2943 adult admissions to 17 SOS Network hospitals and 24 Toronto Invasive Bacterial Disease Network hospitals. Mean age was 69.5 years. Average hospital stay was 10.8 days (95% CI: 10.3, 11.3), general ward stays were 9.4 days (95% CI: 9.0, 9.8), and ICU stays were 9.8 days (95% CI: 8.6, 11.1) for the 14% of patients admitted to the ICU. Average cost per case was $14 612 CAD (95% CI: $13 852, $15 372) including $133 (95% CI: $116, $150) for medical care prior to admission, $14 031 (95% CI: $13 295, $14 768) during initial hospital stay, $447 (95% CI: $271, $624) post-discharge, including readmission within 30 days.

CONCLUSION

The cost of laboratory-confirmed influenza was higher than previous estimates, driven mostly by length of stay and analyzing only laboratory-confirmed influenza cases. The true per-patient cost of influenza-related hospitalization has been underestimated, and prevention programs should be evaluated in this context.

Influenza in Canada, 2012-2013 season

Objective

This report summarizes influenza activity in Canada during the 2012-13 influenza season (August 26, 2012-August 24, 2013) from data obtained through the FluWatch surveillance program.

Methods

FluWatch collected information from six primary indicators of influenza activity that describe the epidemiologic and virologic behaviour of influenza in Canada: sentinel laboratory-based influenza detections; strain characterization and antiviral resistance for circulating influenza viruses; primary care consultation rates of influenza-like illness; regional influenza activity levels; influenza-associated severe outcomes; and pharmacy surveillance.

Results

The influenza season peaked nationally between late December 2012 and early January 2013 with influenza A(H3N2) identified as the predominant circulating influenza strain until early March, when influenza B became the predominant circulating strain. The cumulative reported hospitalization rates for all age groups were 25.0 per 100,000. Influenza A most greatly affected adults ≥65 years of age and influenza B most greatly affected children ≤19 years of age.

Conclusion

The influenza season was moderately severe. When compared to the previous two seasons, which were considered relatively mild, there was a significant increase in laboratory detections for influenza, as well as hospitalizations associated with influenza in 2012-13.

Low 2012-13 influenza vaccine effectiveness associated with mutation in the egg-adapted H3N2 vaccine strain not antigenic drift in circulating viruses

BACKGROUND

Influenza vaccine effectiveness (VE) is generally interpreted in the context of vaccine match/mismatch to circulating strains with evolutionary drift in the latter invoked to explain reduced protection. During the 2012-13 season, however, detailed genotypic and phenotypic characterization shows that low VE was instead related to mutations in the egg-adapted H3N2 vaccine strain rather than antigenic drift in circulating viruses.

METHODS/FINDINGS

Component-specific VE against medically-attended, PCR-confirmed influenza was estimated in Canada by test-negative case-control design. Influenza A viruses were characterized genotypically by amino acid (AA) sequencing of established haemagglutinin (HA) antigenic sites and phenotypically through haemagglutination inhibition (HI) assay. H3N2 viruses were characterized in relation to the WHO-recommended, cell-passaged vaccine prototype (A/Victoria/361/2011) as well as the egg-adapted strain as per actually used in vaccine production. Among the total of 1501 participants, influenza virus was detected in 652 (43%). Nearly two-thirds of viruses typed/subtyped were A(H3N2) (394/626; 63%); the remainder were A(H1N1)pdm09 (79/626; 13%), B/Yamagata (98/626; 16%) or B/Victoria (54/626; 9%). Suboptimal VE of 50% (95%CI: 33-63%) overall was driven by predominant H3N2 activity for which VE was 41% (95%CI: 17-59%). All H3N2 field isolates were HI-characterized as well-matched to the WHO-recommended A/Victoria/361/2011 prototype whereas all but one were antigenically distinct from the egg-adapted strain as per actually used in vaccine production. The egg-adapted strain was itself antigenically distinct from the WHO-recommended prototype, and bore three AA mutations at antigenic sites B [H156Q, G186V] and D [S219Y]. Conversely, circulating viruses were identical to the WHO-recommended prototype at these positions with other genetic variation that did not affect antigenicity. VE was 59% (95%CI:16-80%) against A(H1N1)pdm09, 67% (95%CI: 30-85%) against B/Yamagata (vaccine-lineage) and 75% (95%CI: 29-91%) against B/Victoria (non-vaccine-lineage) viruses.

CONCLUSIONS

These findings underscore the need to monitor vaccine viruses as well as circulating strains to explain vaccine performance. Evolutionary drift in circulating viruses cannot be regulated, but influential mutations introduced as part of egg-based vaccine production may be amenable to improvements.

Brief education to increase uptake of influenza vaccine among pregnant women: a study protocol for a randomized controlled trial

Background

Pregnant women are the highest priority group for annual influenza vaccination. Studies have shown unacceptably low uptake of both seasonal and pandemic A/H1N1 influenza vaccination among pregnant women. This paper will describe the study protocol and methodology of a randomised controlled trial designed to assess the effectiveness of a brief educational intervention in improving the uptake of seasonal influenza vaccine among pregnant women in Hong Kong.

Methods

A randomised controlled trial will be conducted with pregnant women in at least the second trimester of pregnancy from four publicly funded hospital antenatal clinics in Hong Kong. Participants will be randomly assigned to either one of the two treatment groups: standard care (control) or standard care plus brief education (intervention). Pregnant women in the standard care group will receive the usual antenatal care with an educational pamphlet developed by the Hong Kong Centre for Health Protection and those in the intervention group will be provided with usual care plus a brief ten-minute education intervention. Content of the education session will cover four core components recommended in the research literature. The primary study outcome will be the proportion of participants who have received influenza vaccine during their pregnancy. A total of 184 pregnant women (92 per group) will be required to give an 80% power to detect a treatment effect of 15%.

Discussion

Most intervention studies aimed at improving influenza vaccination rates in pregnant women have targeted obstetric-care providers and the results of the two patient-oriented RCT interventions are conflicting. The high priority for vaccination given to pregnant women and the low influenza vaccination rate among pregnant women worldwide strongly indicates a need for interventions to improve uptake.

Trial registration

This trial is registered with the Clinical Trials Registry at www.clinicaltrials.gov(NCT01772901).