Predicted 30‐year protection after vaccination with an aluminum‐free virosomal hepatitis A vaccine

Abstract

Few studies have examined the duration of protection following vaccination against hepatitis A virus (HAV) with currently licensed HAV vaccines. This study explored the long-term immunogenicity in individuals vaccinated with the virosomal hepatitis A virus, Epaxal. Adult volunteers (N = 130) previously enrolled into four different studies between 1992 and 1994 and who had completed a 0/12-month immunization regimen (primary and booster dose) were asked to participate in this follow-up study. Yearly anti-HAV titers up to 6 years following booster vaccination, and then once 9-11 years after booster were measured using two assays, Enzygnost and AxSYM HAVAB 2.0. Based on the Enzygnost assay, the seroprotection rate 9-11 years after booster was 100%, with a geometric mean concentration (GMC) of anti-HAV antibodies of 526 mIU/ml. Females had markedly higher GMCs than males (741 mIU/ml vs. 332 mIU/ml). Using an anti-HAV cut-off titer of >or=10 mIU/ml, a linear mixed mathematical model predicted a median duration of protection of 52.1 years. A duration of protection >or= 35.7 years was predicted for 95% of subjects. A more stringent cut-off of >or=20 mIU/ml shortened the median predicted duration of protection to 45.0 years. In conclusion, a two-dose Epaxal vaccination regimen confers in healthy adults a real-time protection of at least 9-11 years; this protection is predicted to last at least 30 years in over 95% of individuals. Further studies are necessary to assess the real duration of seroprotection and whether an additional booster is necessary later.

Waning of anti-HAV immunity in Shijiazhuang prefecture, Hebei province, China: A comparison of seroprevalence between 1992 and 2011

“…However, we do not know how far the immunity induced by immunization persists, though several studies reported recently that the vaccine induced immunity last as long as vaccines have been available [19][20][21][22]. Therefore, the heterogeneous endemicity over the country [17,18] raised a serious concern of HAV infection, that is, if immunity induced by vaccination decreases when immunized children become adults, the disease burden from hepatitis A will paradoxically increase, because relatively high levels of circulating hepatitis A virus persist.…”

How advances in immunology provide insight into improving vaccine efficacy

“…However, with the milder infection and reduced antigen load associated with vaccination vs. natural infection, the level of long-term immunity may require booster vaccination to reset the plateau phase of antibody production to a new set point that resides above the threshold required for protection (Figure 2). Immunization with live, attenuated hepatitis A vaccine or inactivated hepatitis A vaccine are both capable of eliciting long-term antiviral protection [74] but interestingly, a 2-dose vaccination series with an inactivated whole virus hepatitis A vaccine has been estimated to provide more than 30 years of protective immunity in >95% of vaccinees [75]. A recent study examining the duration of antibody responses following 1, 2, or 3 doses of Cervarix, a highly repetitive non-infectious virus-like particle vaccine against human papilloma virus (HPV), is also particularly informative [76].…”

Successful Memory Response following a Booster Dose with a Virosome-Formulated Hepatitis A Vaccine Delayed Up to 11 Years

“…A single dose of Epaxal, the only aluminum-free virosomal HAV vaccine currently available, is highly immunogenic (3). Two doses of Epaxal administered 12 months apart give adults a real-time protection of at least 9 to 11 years, which is predicted to last for at least 30 years in Ն95% of individuals (4).…”