The inactivated monovalent influenza A(H1N1) vaccines used since the 2009 influenza pandemic, in both the adjuvanted and unadjuvanted forms, were found to be effective in the prevention of influenza and influenza-related hospitalization, according to an international review article published recently in Vaccine.1
The investigators, led by Louise E. Lansbury, PhD, from the Health Protection and Influenza Research Group at the University of Nottingham in the United Kingdom, identified 38 studies published between June 2011 and April 2016 that met inclusion criteria for meta-analysis. Data for evaluation comprised 7,643,738 patient records from multiple different study designs, including test-negative studies (n=13), case control trials (n=10), prospective cohorts (n=7), retrospective evaluations (n=4), screening-method studies (n=2), and systematic reviews (n=2).2-39
The influenza A(H1N1) vaccine was the first to be used internationally in the containment of a pandemic. Overall, the authors found both pandemic vaccines to be “broadly effective” in preventing viral infection and associated hospitalization.
The adjuvanted vaccines were the only type studied in children, where they showed greater efficacy compared with in adults: Pooled adjusted vaccine efficacy in 1126 patients from 2 studies was 86% (95% CI, 67%-94%; P <.00001).8,20 “Adjuvants are immune potentiators, which have been used for decades to enhance, accelerate, and prolong the body’s immune response to vaccine antigens,” Dr Lansbury explained to Infectious Disease Advisor.
Pooled responses to the 2 vaccines indicated only moderate protection of 49% efficacy in 5 studies of people older than 18 years (95% CI, 13%-71%; P =.01; n=3979),2-4,7,24 and neither type reached significance alone. In people older than 50 years, the pooled estimated vaccine efficacy for 2 studies using adjuvanted vaccine was 46% (95% CI, −17% to 75%; P =.22; n=1149).3,7
“Our finding that the pandemic vaccines were not as effective in older people is basically what we see with seasonal flu vaccines in the elderly,” Dr Lansbury reported. She went on to explain that “there were 2 possible reasons for this: 1) That older people had encountered a similar virus to the pandemic H1N1 strain when they were younger, so they were not immunologically naive to the new strain; and 2) that the vaccines simply don’t work as well in older people with less fit immune systems.”
She added, “As we did not see a difference in the effectiveness of unadjuvanted vaccines between adults and children, our results suggest that the adjuvants used in the vaccines in the studies analyzed provoked a stronger immune response in children.”
As previous studies have concluded,40-42 targeting children for pandemic vaccination efforts is a valid strategy.
- Lansbury LE, Smith S, Beyer W, et al. Effectiveness of 2009 pandemic influenza A(H1N1) vaccines: A systematic review and meta-analysis. Vaccine. 2017;35:1996-2006. doi: 10.1016/j.vaccine.2017.02.059
- Griffin MR, Monto AS, Belongia EA, et al. Effectiveness of non-adjuvanted pandemic influenza A vaccines for preventing pandemic influenza acute respiratory illness visits in 4 U.S. communities. PLoS One. 2011;6:e23085-e. doi: 10.1371/journal.pone.0023085
- Andrews N, Waight P, Yung CF, et al. Age-specific effectiveness of an oil-inwater adjuvanted pandemic (H1N1) 2009 vaccine against confirmed infection in high risk groups in England. J Infect Dis. 2011;203:32-39. doi: 10.1093/infdis/jiq014
- Fielding JE, Grant KA, Garcia K,et al. Effectiveness of seasonal influenza vaccine against pandemic (H1N1) 2009 virus, Australia, 2010. Emerg Infect Dis. 2011;17:1181-1187. doi: 10.3201/eid1707.101959
- Hamrin J, Bennet R, Eriksson M, et al. Effectiveness of monovalent adjuvanted vaccine (Pandemrix) for the prevention of hospitalization for influenza A (H1N1)v infection in children. Acta Paediatr. 2010;99:85. doi: 10.1016/j.vaccine.2012.07.009
- Hellenbrand W, Jorgensen P, Schweiger B, Falkenhorst G, Nachtnebel M,Greutélaers B, et al. Prospective hospital-based case-control study to assess the effectiveness of pandemic influenza A(H1N1)pdm09 vaccination and risk factors for hospitalization in 2009-2010 using matched hospital and test-negative controls.. BMC Infect Dis. 2012;12:127. doi: 10.1186/1471-2334-12-127
- Mahmud S, Hammond G, Elliott L, et al. Effectiveness of the pandemic H1N1 influenza vaccines against laboratory-confirmed H1N1 infections: population-based case-control study. Vaccine 2011;29:7975-7981. doi: 10.1016/j.vaccine.2011.08.068
- Ortqvist A, Bennet R, Rinder MR, Lindblad H, Eriksson M. Effectiveness of the monovalent AS03-adjuvanted influenza A(H1N1)pdm09 vaccine against hospitalization in children because of influenza. Vaccine. 2012;30:5699-5702. doi: 10.1016/j.vaccine.2011.08.068
- Puig-Barbera J, Arnedo-Pena A, Pardo-Serrano F, et al. Effectiveness of seasonal 2008–2009, 2009–2010 and pandemic vaccines, to prevent influenza hospitalizations during the autumn 2009 influenza pandemic wave in Castellon, Spain. A test-negative, hospital-based, case-control study. Vaccine. 2010;28:7460-7467. doi: 10.1016/j.vaccine.2010.09.042
- Skowronski DM, Janjua NZ, De Serres G, et al. Effectiveness of AS03 adjuvanted pandemic H1N1 vaccine: case-control evaluation based on sentinel surveillance system in Canada, autumn 2009. BMJ. 2011;342:c7297. doi: 10.1136/bmj.c7297
- Song JY, Cheong HJ, Heo JY, et al. Effectiveness of the pandemic influenza A/H1N1 2009 monovalent vaccine in Korea. Vaccine. 2011;29:1395-1398. doi: 10.1016/j.vaccine.2010.12.050
- Uphoff H, An der Heiden M, Schweiger B, et al. Effectiveness of the AS03-adjuvanted vaccine against pandemic influenza virus A/(H1N1) 2009 – a comparison of two methods; Germany, 2009/10. PLoS One. 2011;6:e19932-e. doi: 10.1371/journal.pone.0019932
- Van Buynder PG, Dhaliwal JK, Van Buynder JL, et al. Protective effect of single-dose adjuvanted pandemic influenza vaccine in children. Influenza Other Respir Viruses. 2010;4:171-178. doi: 10.1111/j.1750-2659.2010.00146.x
- Wijnans L, Dieleman J, Voordouw B, Sturkenboom M. Effectiveness of MF59 adjuvanted influenza A(H1N1)pdm09 vaccine in risk groups in the Netherlands. PLoS One. 2013;8. doi: 10.1371/journal.pone.0063156
- Hadler JL, Baker TN, Papadouka V, et al. Effectiveness of 1 dose of 2009 influenza A (H1N1) vaccine at preventing hospitalization with pandemic H1N1 influenza in children aged 7 months-9 years. J Infect Dis. 2012;206:49-55. doi: 10.1093/infdis/jis306
- Uzicanin A, Thompson M, Smith P, et al; Maine 2009 Influenza A (H1N1) Vaccine Effectiveness Evaluation Group. Effectiveness of 1 dose of influenza A (H1N1) 2009 monovalent vaccines in preventing reverse-transcription polymerase chain reaction-confirmed H1N1 infection among school-aged children in Maine. J Infect Dis. 2012;206:1059-1068. doi: 10.1093/infdis/jis441
- Dominguez A, Castilla J, Godoy P, et al; CIBERESP Cases and Controls in Pandemic Influenza Working Group Spain. Effectiveness of pandemic and seasonal influenza vaccines in preventing pandemic influenza-associated hospitalization. Vaccine. 2012;30:5644-5650. doi: 10.1016/j.vaccine.2012.06.090
- Fu C. Effectiveness of H1N1 vaccine against reported Influenza A (H1N1). Human Vaccines. 2010;6:767-768. doi: 10.4161/hv.6.9.12638
- Gefenaite G, Tacken M, Bos J, et al. Effectiveness of A(H1N1)pdm09 influenza vaccine in adults recommended for annual influenza vaccination. PLoS One. 2013;8:e66125. doi: 10.1371/journal.pone.0066125
- Gilca R, Deceuninck G, De Serres G, et al. Effectiveness of pandemic H1N1 vaccine against influenza-related hospitalization in children. Pediatrics. 2011;128:e1084-1091. doi: 10.1542/peds.2010-3492
- Mahmud SM, Bozat-Emre S, Thompson LH, Elliott LJ, Caeseele P. Effectiveness of the pandemic H1N1 influenza vaccines in preventing hospitalization for influenza and pneumonia: a population-based case-control study. Pharmacoepidemiol Drug Saf. 2013;22:438.
- Steens A, Wijnans EG, Dieleman JP, et al. A/H1N1 influenza-related hospitalisation; a matched case-control study. BMC Infect Dis. 2009;2011:11.
- Thompson MG, Sokolow LZ, Almendares O, et al. Effectiveness of nonadjuvanted monovalent influenza A(H1N1)pdm09 vaccines for preventing reverse transcription polymerase chain reaction-confirmed pandemic influenza hospitalizations: case-control study of children and adults at 10 US influenza surveillance network sites. Clin Infect Dis. 2013;57:1587-1592. doi: 10.1093/cid/cit551
- Zhang Y, Seale H, Yang P, et al. Factors associated with the transmission of pandemic (H1N1) 2009 among hospital healthcare workers in Beijing, China. Influenza Other Respir Viruses. 2013;7:466-471. doi: 10.1111/irv.12025
- Emborg HD, Krause TG, Hviid A, Simonsen J, Mølbak K. Effectiveness of vaccine against pandemic influenza A/H1N1 among people with underlying chronic diseases: cohort study, Denmark, 2009-10. BMJ. 2012;344:d7901. doi: 10.1136/bmj.d7901
- Guzman Herrador BR, Aavitsland P, Feiring B, Riise Bergsaker MA, Borgen K. Usefulness of health registries when estimating vaccine effectiveness during the influenza A(H1N1)pdm09 pandemic in Norway. BMC Infect Dis. 2012;12:63. doi: 10.1186/1471-2334-12-63
- Lim J, Choi B, Kim J, et al. Evaluation and sensitivity analysis of the effectiveness of unadjuvanted A(H1N1)pdm09 vaccine in hospital workers using multi-center cohort study in Korea. Vaccine. 2013;31:2381-2386. doi: 10.1016/j.vaccine.2013.02.066
- Wu J, Xu F, Lu L, et al. Safety and effectiveness of a 2009 H1N1 vaccine in Beijing. N Engl J Med. 2010;363:2416-2423. doi: 10.1056/NEJMoa1006736
- Costa JT, Silva R, Tavares M, Nienhaus A. High effectiveness of pandemic influenza A (H1N1) vaccination in healthcare workers from a Portuguese hospital. Int Arch Occup Environ Health. 2012;85:747-752. doi: 10.1007/s00420-011-0714-8
- He HQ, Li Q, He B, et al. Epidemiological effects of the A (H1N1) influenza vaccine immunization program on students. Zhonghua Liu Xing Bing Xue Za Zhi 2011;32:661-663. doi: 10.3760/cma.j.issn.0254-6450.2011.07.005
- Lee VJ, Tan CH, Yap J, et al. Effectiveness of pandemic H1N1-2009 vaccination in reducing laboratory confirmed influenza infections among military recruits in tropical Singapore. PLoS One. 2011;6:e26572. doi: 10.1371/journal.pone.0026572
- Njuguna H, Ahmed J, Oria PA, et al. Uptake and effectiveness of monovalent influenza A (H1N1) pandemic 2009 vaccine among healthcare personnel in Kenya, 2010. Vaccine. 2013;31:4662-4667. doi: 10.1016/j.vaccine.2013.07.005
- Ortqvist A, Berggren I, Insulander M, de Jong B, Svenungsson B. Effectiveness of an adjuvanted monovalent vaccine against the 2009 pandemic strain of influenza A(H1N1)v, in Stockholm County, Sweden. Clin Infect Dis. 2011;52:1203-1211. doi: 10.1093/cid/cir182
- Schuurmans MM, Tini GM, Dalar L, Fretz G, Benden C, Boehler A. Pandemic 2009 H1N1 influenza virus vaccination in lung transplant recipients: coverage, safety and clinical effectiveness in the Zurich cohort. J Heart Lung Transplant. 2011;30:685-690. doi: 10.1016/j.healun.2011.01.707
- Syrjanen RK, Jokinen J, Ziegler T, et al. Effectiveness of pandemic and seasonal influenza vaccines in preventing laboratory-confirmed influenza in adults: A clinical cohort study during epidemic seasons 2009–2010 and 2010–2011 in Finland. PLoS One. 2014;9:e108538. doi: 10.1371/journal.pone.0108538
- Seyler T, Bella A, Puzelli S, Rizzo C; Screening Method Working Group. Screening method working group. Estimating pandemic vaccine effectiveness in two Italian regions using the screening method, 2009–2010. Vaccine. 2012;30:109-111. doi: 10.1016/j.vaccine.2011.11.013
- Wichmann O, Stocker P, Poggensee G, et al. Pandemic influenza A(H1N1) 2009 breakthrough infections and estimates of vaccine effectiveness in Germany 2009–2010. Euro Surveill. 2010;15. pii: 19561.
- Yin JK, Chow MY, Khandaker G, et al. Impacts on influenza A(H1N1)pdm09 infection from cross-protection of seasonal trivalent influenza vaccines and A(H1N1)pdm09 vaccines: systematic review and metaanalyses. Vaccine 2012;30:3209–3222. doi: 10.1016/j.vaccine.2012.02.048.
- Osterholm MT, Kelley NS, Sommer A, Belongia EA. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. Lancet Infect Dis. 2012;12:36-44. doi: 10.1016/S1473-3099(11)70295-X
- Lee S, Golinski M, Chowell G. Modeling optimal age-specific vaccination strategies against pandemic influenza. Bull Math Biol. 2012;74:958-980. doi: 10.1007/s11538-011-9704-y
- Shim E. Prioritization of delayed vaccination for pandemic influenza. Math Biosci Eng. 2011;8:95-112. doi: 10.3934/mbe.2011.8.95
- Nakanishi M, Yoshida Y, Takeda N, et al. Community-acquired pneumonia distinguished from influenza infection based on clinical signs and symptoms during a novel (swine) influenza. Prim Care Respir J. 2011;20:421-426. doi: 10.4104/pcrj.2011.00067