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Vaccine. 2017 Jan 5;35(2):212-221. doi: 10.1016/j.vaccine.2016.11.013. Epub 2016 Dec 7.

Do antibody responses to the influenza vaccine persist year-round in the elderly? A systematic review and meta-analysis.

Author information

1
Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, 308433 Singapore, Singapore. Electronic address: Barnaby_young@ttsh.com.sg.
2
Saw Swee Hock School of Public Health, Tahir Foundation Building, National University of Singapore, 12 Science Drive 2, #09-01, 117549 Singapore, Singapore.
3
Saw Swee Hock School of Public Health, Tahir Foundation Building, National University of Singapore, 12 Science Drive 2, #09-01, 117549 Singapore, Singapore; Yale-NUS College, National University of Singapore, 16 College Avenue West #01-220, 138527 Singapore, Singapore.
4
School of Tropical Medicine and Global Health, Nagasaki University Institute of Tropical Medicine, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan; London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
5
Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, 308433 Singapore, Singapore; Lee Kong Chian School of Medicine, 11 Mandalay Road, 308232 Singapore, Singapore.
6
Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, 308433 Singapore, Singapore; Saw Swee Hock School of Public Health, Tahir Foundation Building, National University of Singapore, 12 Science Drive 2, #09-01, 117549 Singapore, Singapore.

Abstract

INTRODUCTION:

The influenza vaccine is less immunogenic in older than younger adults, and the duration of protection is unclear. Determining if protection persists beyond a typical seasonal epidemic is important for climates where influenza virus activity is year-round.

METHODS:

A systematic review protocol was developed and registered with PROSPERO [CRD42015023847]. Electronic databases were searched systematically for studies reporting haemagglutination-inhibition (HI) titres 180-360days following vaccination with inactivated trivalent seasonal influenza vaccine, in adults aged ⩾65years. Geometric mean titre (GMT) and seroprotection (HI titre ⩾1:40) at each time point was extracted. A Bayesian model was developed of titre trajectories from pre-vaccination to Day 360. In the meta-analysis, studies were aggregated using a random-effects model to compare pre-vaccination with post-vaccination HI titres at Day 21-42 ('seroconversion'), Day 180 and Day 360. Potential sources of bias were systematically assessed, and heterogeneity explored.

RESULTS:

2864 articles were identified in the literature search, of which nineteen met study inclusion/exclusion criteria. Sixteen studies contained analysable data from 2565 subjects. In the Bayesian model, the proportion of subjects seroprotected increased from 41-51% pre-vaccination to 75-78% at seroconversion. Seroprotection subsequently fell below 60% for all serotypes by Day 360: A/H1 42% (95% CI 38-46), A/H3 59% (54-63), B 47% (42-52). The Bayesian model of GMT trajectories revealed a similar pattern. By Day 360, titres were similar to pre-vaccination levels. In the meta-analysis, no significant difference in proportion of subjects seroprotected, 0 (-0.11, 0.11) or in log2GMT 0.30 (-0.02, 0.63) was identified by Day 360 compared with pre-vaccination. The quality of this evidence was limited to moderate on account of significant participant dropout.

CONCLUSIONS:

The review found consistent evidence that HI antibody responses following influenza vaccination do not reliably persist year-round in older adults. Alternative vaccination strategies could provide clinical benefits in regions where year-round protection is important.

KEYWORDS:

Elderly; Influenza; Seasonal; Seroprotection; Tropics; Vaccine

PMID:
27939013
DOI:
10.1016/j.vaccine.2016.11.013
[Indexed for MEDLINE]
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