Infectious Disease

Continued efforts are needed for the completion of the vaccination schedule among immunocompromised patients, in particular HIV-positive men who have sex with men, to prevent vaccine variants from escaping the protective effect of vaccines, according to researchers from Barcelona, Spain.

“An incomplete vaccination schedule in an immunocompromised host could lead to a situation of only partial protection, providing suitable conditions for the emergence of an antigenic variant,” they wrote.

The researchers identified six hepatitis A virus antigenic variants that may have escaped the protective effect of available vaccines among 128 virus isolates characterized during 2005 and 2009. Two were V1171A and A1280V variants, and four were V1166G, Y1181S, R1189T, and A1280E variants.

Four variants were pooled from men who have sex with men during an outbreak including 186 reported cases between 2008 and 2009. Only eight of the reported cases in MSM were vaccinated of which only one case reported completion of the vaccination schedule.

“Hepatitis A virus is a genetically stable virus in comparison with other RNA viruses, with a single serotype so far described,” Albert Bosch, study researcher, in the department of microbiology at Enteric Virus Laboratory, and the Institute of Nutrition and Food Safety at the University of Barcelona, told Infectious Disease News. “However, in some situations, such as the one mentioned above with improperly vaccinated immunocompromised hosts, a mutant virus may emerge. The immunocompromised population may act as reservoir for the emergence of virus variants if vaccination schedules are not thoroughly completed.” – by Ashley DeNyse

Disclosures: The researchers report no relevant financial disclosures.

The recommendation is that all such persons be fully vaccinated to prevent emergence and potential transmission of such a virus. This is different from the issues I have raised here, which have to do with changes in the ecosystem due to use of the vaccine. Assuming that mutated hepatitis A virus has emerged and is transmissible, to what extent will the available vaccine prevent infection with mutated strains of hepatitis A? Additionally, can use of the vaccine change the ecosystem in ways that could enhance emergence and transmission of mutated hepatitis A virus not covered by the vaccine? Vaccine-associated changes to the micro-organism ecosystem were observed following adoption of the pneumococcal conjugate vaccine (Prevnar-7, Wyeth), which eventually required developing Prevnar-13 to cover antibiotic-resistant strains of pnemococcus, such as serotype 19A. These are the sort of issues related to effectiveness and efficacy that are of great concern to the public.

– Vicky Pebsworth Debold, PhD, RN
Director of Patient Safety, National Vaccine Information Center, VA

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