The secondary attack rate of hepatitis A virus (HAV) among contacts of cases is up to 50%.

Background: The secondary attack rate of hepatitis A virus (HAV) among contacts of cases is up to 50%.

Historically, contacts were offered immunoglobulin (IG, a human derived blood product) as post-exposure prophylaxis (PEP). Amid safety concerns about IG, HAV vaccine is increasingly recommended instead. Public health authorities’ recommendations differ, particularly for healthy contacts ≥40 years old, where vaccine efficacy data is limited. We evaluated routine use of HAV vaccine as an alternative to immunoglobulin in PEP, in those considered at low risk of severe infection in the Netherlands.

Methods: Household contacts of acute HAV cases notified in Amsterdam (2004-2012) were invited ≤14 days post-exposure, for baseline anti-HAV testing and PEP according to national guidelines: immunoglobulin if at risk of severe infection, or hepatitis A vaccine if healthy and at low risk (aged <30, or, 30-50 years and vaccinated <8 days post-exposure).  Incidence of laboratory confirmed secondary infection in susceptible contacts was assessed 4-8 weeks post-exposure. 

Results: Of 547 contacts identified, 191 were susceptible to HAV. Per-protocol, 167 (87%) were vaccinated with HAV vaccine and 24 (13%) were given immunoglobulin.  At follow-up testing, 8 had a laboratory confirmed infection of whom 7 were symptomatic.

Q1. What is the secondary attack rate of hepatitis A?

Q2. What is the secondary attack rate of symptomatic hepatitis A?