Evidence for Hepatitis A virus endemic circulation in Israel despite universal toddlers' vaccination since 1999 and low clinical incidence in all age groups.

Background: Universal toddlers vaccination (UTV) introduced in 1999, reduced hepatitis A incidence in Israel from 50.4 to <1.0/100,000. The current Hepatitis A virus (HAV) molecular epidemiology in Israel was studied 13-14y post UTV introduction..

Methods: An outbreak in Tel-Aviv with 75 cases in 2012-2013 was investigated. Real-time RT-PCR and sequencing of the VP1-2A region (1100bp) was done on: a. serum samples from patients with acute Hepatitis A (12/ 75 in Tel-Aviv and 31 patients hospitalized in 3 other major cities in 2011-2013); b. in sewage samples (27 from metropolitan Tel-Aviv, 14 from the other 3 cities and 6 from Gaza).

Results: The outbreak began among intravenous drug users then spread to the general population. Patients' mean age was 33.2y, 4/75(5.3%) had been vaccinated and 58/75(77.3%) were hospitalized. No common environmental source was found. HAV was detected in sewage samples: 16/27(59.2%) from Tel-Aviv; 4/14(28.6%) collected throughout Israel and 6/6 (100%) from Gaza. Genotype IB predominated (52/53 sequenced samples) and identical strains were demonstrated in the Israeli and Palestinian populations by phylogenetic analysis.

Conclusions: Despite the UTV success, HAV circulation in the Israeli population continues, apparently due to its close contacts with the endemic Palestinian population. Reassessment of vaccination policy is recommended.