Clinical

For post-exposure prophylaxis, hep A vaccine works better in young adults

Last Updated: 2013-11-04 10:12:27 -0400 (Reuters Health)

By C. Vidya Shankar MD

NEW YORK (Reuters Health) - Giving the hepatitis A vaccine within two weeks of contact is effective for post-exposure prophylaxis (PEP) -- but only in adults under age 40, a new study shows.

The risk of secondary infection is many fold greater when the vaccine is used in older adults, researchers from The Netherlands reported online October 17th in PLoS One.

Lead author Dr. Jane Whelan, from the Amsterdam Public Health Service, told Reuters Health by email, "In people over 40 years of age (and in those otherwise at risk of severe disease), we recommend that human immunoglobulin should be the PEP of choice."

"In healthy people under 40 years, hepatitis A vaccine is the best option post-exposure because it protects immediately and additionally gives long-term protection," she said.

In The Netherlands, from 2004 onward, close contacts under age 30 received the hepatitis A vaccine, while those over 50 received hepatitis A immunoglobulin. Those aged between 30 and 50 and reporting within eight days of contact were given the vaccine, while those reporting after eight days received immunoglobulin, according to the researchers' paper.

Vaccine timing took into account the incubation period of hepatitis A of 15-50 days, the authors note.

Appearance of jaundice was taken as onset of illness. Close contacts were defined as those living within the same household. Contacts were tested for anti-hepatitis A antibodies and offered a single dose of the hepatitis A vaccine or intramuscular immunoglobulin. Those with negative anti-hepatitis A antibodies were considered susceptible to infection.

Of the 191 susceptible contacts of 200 hepatitis A patients who agreed to prophylaxis, 167 received the hepatitis A vaccine and 24 received anti-hepatitis A immunoglobulins within six and 10 days of contact, respectively.

Seven contacts, three of them over 40, developed symptomatic hepatitis A infection despite vaccine prophylaxis. However, no contact who received immunoglobulin developed hepatitis A.

"The vaccine may not be as effective in preventing secondary infection in people aged over 40 years compared to younger people," Dr. Whelan commented in her email.

Hepatitis A secondary infection rates among contacts were 3% among those under age 15, 6% in the 16-40 age group, and 30% among those over 40, with corresponding relative risks of 1, 1.8 and 12 respectively).

The researchers admit that their sample size was underpowered because of the small number of secondary infections. Nevertheless, they say, "Our findings suggest that a more conservative upper age limit for contact vaccination may be appropriate."

"This real-world evaluation illustrates the complexities of post-exposure prophylaxis in a low-endemic country where there are high levels of preexisting immunity," the researchers point out.

They conclude, "Retaining the use of immunoglobulin as PEP of choice in older people and those at risk of severe illness seems appropriate."

SOURCE: http://bit.ly/1cGJbiz

PLoS One 2013.