Recommendations from the National Varicella Consensus Conference: SURVEILLANCE NEEDS

Additional/improved data needs

Recommendation 5.1: All provinces should have a surveil­lance system that can provide information on the number and age distribution of cases of both varicella and herpes zoster. Recommendation 5.2: Canadian data should be gathered on the epidemiology and burden of illness in pregnancy. This should include gestational varicella and herpes zoster; perinatal varicella (maternal and infant); and congenital varicella syndrome (add to the Canadian Paediatric Sur­veillance Program as active surveillance). Recommendation 5.3: National population-based data should be gathered on the incidence of severe disease, particu­larly in adults, including hospitalizations and deaths.

Recommendation 5.4: Varicella and herpes zoster should be added to the Vital Statistics List of Rare and Infrequent Causes of Death.

Surveillance goals

Recommendation 5.5: A goal should be adopted to detect changes in the age-specific incidence of varicella.

The specific strategies/methods to achieve the specified goal are as follows:

  • Implementation phase: aggregate reporting, using sources such as schools, nurseries, daycare centres, emergency departments, walk-in clinics, sentinel physicians and health claims data.
  • Control phase: case-by-case reporting, including enhanced sentinel surveillance and outbreak investigation and control (with laboratory confirmation of cases, differentiation of wild versus vaccine virus strains, and serological testing).

Recommendation 5.6: A goal should be adopted to describe changes in frequency and risk factors for severe varicella dis­ease (defined as hospitalization or death due to chickenpox or an associated complication).

The specific strategies/methods to achieve the specified goal are as follows:

  • A sentinel hospital-based system, including the following components

–   paediatric: use revised Immunization Monitoring Program, ACTive (IMPACT) surveillance;

–   adult: use existing systems (eg, Canadian Hospital Epidemiology Committee, Canadian Infectious Disease Society, Community Hospital Infection Control Association – Canada) to identify patients and collect data;

–   report cases to provincial/territorial epidemiologists;

–  collate data at a national level.

  • Laboratory differentiation of VZV strains (wild type versus vaccine strain).
  • For deaths, a review of the vital statistics database.

Recommendation 5.7: A goal should be adopted to monitor changes in the epidemiology of herpes zoster.

The specific strategies/methods to achieve the specified goal are as follows:

  • Implementation phase: to continue baseline monitoring and, for childhood herpes zoster, establish case-by-case reporting (through the Canadian Paediatric Surveillance Program) and laboratory differentiation of wild type versus vaccine virus strains.
  • Control phase: to continue baseline monitoring and initiate case-by-case reporting for adults aged 20 to 50 years through sentinel physicians and hospital-based reporting.

Recommendation 5.8: A goal should be adopted to measure vaccine coverage in targeted populations.

The specific strategies/methods to achieve the specified goal are as follows:

  • to add varicella vaccine to the annual National Vaccine Coverage Survey;
  • to utilize existing registries such as the provincial immunization registries and the national network of registries;
  • to adjust coverage estimates for prior disease (which would result in falsely low coverage) if indicated, based on vaccine target population.

Recommendation 5.9: A goal should be adopted to monitor vaccine safety.

The specific strategies/methods to achieve the specified goal are as follows:

  • to use existing systems to monitor vaccine-associated adverse events;
  • to monitor childhood herpes zoster post-vaccination (see Recommendation 5.7);
  • to monitor transmission of vaccine virus to contacts; if disease is severe, case-by-case investigation should be carried out (see Recommendation 5.6);
  • to report inadvertent vaccination of pregnant women to existing pregnancy registries (eg, manufacturer-based registries, Motherisk);
  • to monitor the inadvertent vaccination of pregnant women by adding a question regarding prior vaccine exposure to the prenatal form.

Recommendation 5.10: A goal should be adopted to measure vaccine effectiveness in the field.

The specific strategies/methods to achieve the specified goal are as follows:

  • Implementation phase: selected outbreak investigation among vaccinated populations.
  • Implementation phase: special studies (seroepidemiology among immunized populations, immunogenicity under field conditions).
  • Control phase: investigation of disease in vaccinated individuals.

Recommendation 5.11: A goal should be adopted to ensure laboratory capacity for VZV testing to support surveillance.

The specific strategies/methods to achieve the specified goal are as follows:

  • to have in place a readily available laboratory capacity (ie, a provincial laboratory or a reference laboratory) to confirm the diagnosis of VZV infection as needed, and to determine susceptibility to VZV as needed;
  • to establish a national reference laboratory to perform strain characterization and to ensure quality assurance.

Recommendation 5.12: A goal should be adopted to dissemi­nate surveillance data.

The specific strategies/methods to achieve the specified goal are as follows:

  • each province/territory should have a system in place for regular, timely dissemination of surveillance data;
  • to compile surveillance data at the national level as part of the annual immunization report;
  • to add varicella updates to LCDC’s web site during the implementation phase.

Recommendation 5.13: The surveillance methods should be evaluated.
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  • Ongoing evaluations of the surveillance systems should be built in by those responsible for the systems.
  • Periodic special studies should be conducted to ensure the validity of the data.
  • Regular surveys of users of surveillance systems should be conducted to evaluate ease of use of the system, and the suitability and utility of the data.
  • The systems should be modified or new systems developed as gaps are identified by users and expert groups.

Category: Main

Tags: National Varicella, PUBLIC HEALTH, VARICELLA VACCINE

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