Table. Summary of key differences in case and exposure ascertainment for syndromic and virological surveillance and vaccine effectiveness estimation, four southern hemisphere countries, 2019 influenza season.
| Characteristic | Australia | Chile | New Zealand | South Africa |
|---|---|---|---|---|
| Source populationsa | ILI: 394 GPs at sentinel general practices nationwide participate in syndromic ILI surveillance; 222 GPs participate in swab testing; 21 sentinel hospitals nation-wide | Seven sentinel hospitals in 6/16 regions | 86 sentinel practices (ILI patients) in 20 district health boards and four hospitals (SARI patients) | Syndromic: a healthcare provider network Virological and VE: Sentinel general practices (ILI patients) in 6/9 regions |
| Period used for weekly rates | ILI: weeks 1–52 2019: weeks 1–39 Hospitals: weeks 14–44 2019: weeks 14–39 |
Weeks 1–52 2019: weeks 10–33 |
Weeks 18–39 2019: weeks 18–39 |
Weeks 1–52 2019: weeks 1–38 |
| Clinical case definition | ILI: fever or history of fever AND cough, fatigue/malaise Hospitals: suspected influenza (not SARI) |
SARI: history of fever, or measured fever of ≥ 38 C° AND cough AND onset within the last 10 days AND hospitalisation | ILI: acute respiratory illness with a history of fever or measured fever of ≥ 38 °C, AND cough, AND onset within the past 10 days SARI: as above, but requiring hospitalisation |
ILI: measured fever (≥ 38 °C) or history of fever, cough, onset ≤ 10 days |
| Virological testing | ILI: Around 50% of patients are swabbed for testing by RT-PCR at SA Pathology, Adelaide or the NIC, Melbourne. Hospitals: RT-PCR testing done at each hospital. Sequencing performed by WHOCCRRI, Melbourne. |
RT-PCR or direct immunofluorescence followed by RT-PCR-positive for pan-negative and influenza-positive specimens for subtyping. Testing and sequencing performed at NIC, Santiago. |
RT-PCR testing at NIC, Wellington. Sequencing performed by WHOCCRRI, Melbourne. |
RT-PCR testing by NIC, Johannesburg. Sequencing performed by WHOCCRRI, Melbourne or Worldwide Influenza Centre, Crick Institute, London. |
| Study period for VE estimation | ILI: 28 Apr 2019–9 Oct 2019 Hospitals: 1 Apr 2019–16 Aug 2019 |
SARI: 4 Mar 2019–18 Aug 2019 | ILI and SARI: 29 Apr 2019–29 Sep 2019 | ILI: 15 Apr 2019–18 Aug 2019 |
| Cases/controls for VE estimates | ILI: test-positive cases vs test-negative controls Hospitals: test-positive cases; control are the next admitted test-negative patient (≤ 2 weeks) |
Test-positive cases vs test-negative controls | Test-positive cases vs test-negative controls | Test-positive cases vs test-negative controls |
| Vaccination status ascertainment | Medical record, self-report or vaccination registry | Medical record or vaccination registries (no verbal reports) | Vaccination registry and self-report | Medical record or self-reported |
| Vaccination coverage among influenza-negative controls included in VE estimatesb | Overall: 49% ILI; 47% hospitals Adults: 46% ILI; 41% hospitals Children: 26% ILI; 33% hospitals Elderly: 78% ILI; 73% hospitals |
Overall: 61% SARIc
Adults: 41% SARIc Children: 72% SARIc Elderly: 64% SARIc |
Overall: 26% ILI; 33% SARI Adults: 26% ILI; 36% SARI Children: 9% ILI Elderly: 70% ILI; 66% SARI |
Overall: 11% ILI Adult: 11% ILI Children: 9% ILI Elderly: 35% ILI |
| Vaccines licensed | < 5 years: Flu Quadri Junior (Sanofi) < 65 years: Afluria Quad (Seqirus), FluQuadri (Sanofi) and Fluarix Tetra (GSK) ≥ 65 years: Fluad (Seqiris; trivalent with B/Yamagata component) |
Influvac (Abbott) (inactivated subunit vaccine) TIV included a B/Victoria-lineage component |
6–35 months: Fluarix Tetra (GSK) ≥ 3 years: FluQuadri (Sanofi), Influvac (Abbott) ≥ 5 years only: Afluria Quad (Seqiris) |
Vaxigrip (Sanofi Pasteur) (inactivated split-virion vaccine) and Influvac (Abbott) (inactivated subunit vaccine) All TIV |
| Target groups for vaccination | Recommended for all. Free for pregnant women; people aged < 5 years or ≥ 65 years; Aboriginal and Torres Strait Islander peoples; people aged 5–64 years with chronic conditions. |
Pregnant women from 13 weeks gestation; children aged 6–59 months, adults aged ≥ 65 years; poultry and pig farm workers; patients with chronic conditions aged 5– 64 years; carriers of some risk conditions; healthcare workers. | Pregnant women; people aged ≥ 65 years; people aged < 65 years with a medical condition that increases their risk of developing complications from influenza and the condition is specified in the Influenza Immunisation Programme eligibility criteria; children aged ≤ 4 years with previous hospitalisation for respiratory illness or with a history of significant respiratory illness. | Pregnant women at all stages of pregnancy, including the post-partum period; HIV-infected individuals; adults or children who are at high risk for influenza complications because of underlying medical conditions or who are receiving regular medical care for conditions such as chronic pulmonary disease; persons aged ≥ 65 years. |
GP: general practice; GSK: Glaxo Smith Kline; ILI: influenza-like illness; NIC: National Influenza Centre; QIV: quadrivalent inactivated vaccine; SARI: severe acute respiratory illness; TIV: trivalent inactivated vaccine; VE: vaccine effectiveness; WHOCCRRI: World Health Organization Collaborating Centre for Reference and Research on Influenza.
a Numbers are provided for 2019.
b Children: 6 months–17 years of age; Adults: 18–64 years of age; Elderly: ≥ 65 years of age.
c Only patients in a target group for vaccination are included in SARI surveillance in Chile so these numbers do not necessarily reflect coverage in the whole population.