Immunization Dialogue

Indian Pediatrics 2001; 38: 301-302  

The views expressed by Prof. T. Jacob John in this section are personal in nature and should not be construed as the official stand of the Indian Academy of Pediatrics. –Editor-in-Chief

Protection Provided by Hepatitis B Vaccine

There is a steep rise in the anti HBs titer after the third dose of vaccine, as compared to the levels achieved after first and second doses of Hepatitis B vaccine. What percent-age of the vaccinees remain vulnerable during the interval between the second and the third doses of the vaccine?

Yash Paul,
A-D-7, Devi Marg,
Bani Park, Jaipur 302 016,
India.

Generally speaking, we may assume that 100% subjects are (theoretically) vulnerable to virus infection before vaccination, but they need not be at risk. We must presume that most of them will continue to be non-immune even after the first dose of hepatitis B vaccine, but before the second dose. In many studies, the seroconversion rates have been high after the second dose. The protective level of antibody (>10 mIU/ml) would have been reached by most of them. Therefore we must presume that the vast majority of subjects are immune. It would not be possible to measure the protective efficacy in this interval. If the third dose is given on time, then the antibody levels would be very high and the protective level of antibody will be retained for several years. If the third dose is not given, then the antibody levels tend to decline rapidly and we may assume that a large proportion would become vulnerable (immunologically) after one or more years. Therefore we recommend the third dose 5 months after the second dose.

T. Jacob John,
439, Civil Supplies Godown Lane,
Kamalakshipuram,
Vellore TN 632 002,
India.
E-mail: [email protected]