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Clin Infect Dis. 2018 Oct 11. doi: 10.1093/cid/ciy737. [Epub ahead of print]

Influenza Vaccine Effectiveness in Preventing Influenza-associated Hospitalizations During Pregnancy: A Multi-country Retrospective Test Negative Design Study, 2010-2016.

Author information

1
Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
2
Institute for Clinical Evaluative Sciences.
3
Public Health Ontario.
4
Department of Family and Community Medicine.
5
Dalla Lana School of Public Health, University of Toronto.
6
University Health Network, Toronto, Ontario, Canada.
7
School of Public Health, Curtin University, Perth.
8
Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, Subiaco, Western Australia, Australia.
9
Chief Physician's Office, Clalit Health Services, Clalit Research Institute, Tel Aviv.
10
School of Public Health, Medical School for International Health, Ben Gurion University, Bersheva, Israel.
11
University of Michigan School of Public Health, Ann Arbor.
12
University of Alberta.
13
ProvLab Alberta, Edmonton, Canada.
14
Kaiser Permanente Vaccine Study Center, Kaiser Permanente Northern California, Oakland.
15
Communicable Disease Control Directorate, Department of Health Western Australia, Perth, Australia.
16
Cumming School of Medicine, University of Calgary.
17
Alberta Health, Edmonton, Canada.
18
Abt Associates, Cambridge, Massachusetts.
19
Kaiser Permanente Washington Health Research Institute, Seattle, Washington.
20
School of Epidemiology and Public Health, University of Ottawa.
21
Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada.
22
Department of Microbiology, QEII Medical Centre, PathWest Laboratory Medicine, Nedlands, Western Australia, Australia.
23
Division of Preventive Medicine.
24
School of Public Health, University of Alberta, Edmonton.
25
Department of Community Health Sciences, University of Calgary, Alberta, Canada.
26
Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon.

Abstract

Background:

To date, no study has examined influenza vaccine effectiveness (IVE) against laboratory-confirmed influenza-associated hospitalizations during pregnancy.

Methods:

The Pregnancy Influenza Vaccine Effectiveness Network (PREVENT) consisted of public health or healthcare systems with integrated laboratory, medical, and vaccination records in Australia, Canada (Alberta and Ontario), Israel, and the United States (California, Oregon, and Washington). Sites identified pregnant women aged 18 through 50 years whose pregnancies overlapped with local influenza seasons from 2010 through 2016. Administrative data were used to identify hospitalizations with acute respiratory or febrile illness (ARFI) and clinician-ordered real-time reverse transcription polymerase chain reaction (rRT-PCR) testing for influenza viruses. Overall IVE was estimated using the test-negative design and adjusting for site, season, season timing, and high-risk medical conditions.

Results:

Among 19450 hospitalizations with an ARFI discharge diagnosis (across 25 site-specific study seasons), only 1030 (6%) of the pregnant women were tested for influenza viruses by rRT-PCR. Approximately half of these women had pneumonia or influenza discharge diagnoses (54%). Influenza A or B virus infections were detected in 598/1030 (58%) of the ARFI hospitalizations with influenza testing. Across sites and seasons, 13% of rRT-PCR-confirmed influenza-positive pregnant women were vaccinated compared with 22% of influenza-negative pregnant women; the adjusted overall IVE was 40% (95% confidence interval = 12%-59%) against influenza-associated hospitalization during pregnancy.

Conclusion:

Between 2010 and 2016, influenza vaccines offered moderate protection against laboratory-confirmed influenza-associated hospitalizations during pregnancy, which may further inform the benefits of maternal influenza vaccination programs.

PMID:
30307490
DOI:
10.1093/cid/ciy737

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