NANJING and KUNMING, CHINA—The first two vaccines against the C4 strain of human enterovirus 71 appear to protect children against hand, foot and mouth disease and herpangina, also known as mouth blisters
Two phase III studies reported in the New England Journal of Medicine that a year after having two doses of either vaccine (both of them inactivated whole-virus vaccines) 99 per cent of children developed antibodies against the virus.
The two studies —with a total of 22 000 children under six — were not able to show efficacy against the more serious neurological disorders like encephalitis which are caused by enterovirus 71 infection, however (which can appear at those young ages).
Dr Peter McMinn MD, PhD, from the University of Sydney writer of the accompanying editorial comment said, however, that since fewer than 1 per cent of children who get infected develop the severe diseases like encephalitis neither study was powered to demonstrate protection against them: “But it’s likely that the vaccine will prevent [them] because it’s preventing infection, but it will really require much longer surveillance after the vaccines are put on the market to really establish that very clearly,” he noted.
Dr. McMinn also noted that even if these vaccines appear effective against the one strain of EV 71 (such as the one that’s caused most epidemics in South East Asia — the C4 strain) they do not provide cross-protection against other circulating lineages or against coxsackievirus A16 infection, which also triggers the same syndromes.
“If you look at all of the strains that have been circulating in South East Asia, neither vaccine protects against all of those. So there is a need, in the longer term, to broaden out the strain types present in the vaccine and ultimately the vaccine also needs to include a strain that will protect against coxsackievirus A16,” he said.
SOURCE 1: Zhu F. et al., Efficacy, Safety, and Immunogenicity of an Enterovirus 71 Vaccine in China, NEJM, 2014;370:818-28.DOI: 10.1056/NEJMoa1304923.
LINK 1: http://www.nejm.org/doi/full/10.1056/NEJMoa1304923
SOURCE 2: Rongcheng L. et al., An Inactivated Enterovirus 71 Vaccine in Healthy Children, NEJM, 2014;370:829-37. DOI: 10.1056/NEJMoa1303224.
LINK 2: http://www.nejm.org/doi/full/10.1056/NEJMoa1303224
SOURCE 3: McMinn Peter C., Enterovirus Vaccines for an Emerging Cause of Brain-Stem Encephalitis, NEJM, 2014;370:792-94.DOI: 10.1056/NEJMp1400601.
LINK 3: http://www.nejm.org/doi/full/10.1056/NEJMp1400601
AUTHOR: Dr. Peter McMinn. MD PhD,
Professor of infectious diseases medicine, University of Sydney, Australia