Interpretation of the Hib vaccine response

DTaP-IPV-Hib, or the 5-in-1 vaccine, includes a vaccine component that protects against Hib diseases. The 5-in-1 vaccine is administered to young children as part of the national vaccination programme at the age of 3, 5 and 12 months.

In certain situations, a separate Hib vaccine may be used to supplement the vaccination cover of a child under five years of age. This vaccine is also used to protect those who are particularly susceptible to infections caused by Hib bacteria due to an underlying disease or treatment, for instance splenectomy patients.

Issues to consider when taking samples

The antibody response to a Hib vaccine develops within 4 weeks of vaccination. For this reason, a serum sample should be extracted no earlier than 4 weeks after vaccination, but no later than within 2 months.

Interpretation of the Hib vaccine response

In the interpretation of the vaccine response, the subject is considered to have developed a sufficiently good antibody response when the antibody concentration after vaccination is ≥ 1 μg/ml. This threshold is based on a demographic study where an antibody level ≥ 1 µg/ml seemed to predict a high level of protection against invasive Hib disease [1]. 

However, it should be noted that, based on an individual's antibody concentration, it cannot be directly determined whether the person has protection against Hib diseases. This is due to the fact that individual characteristics such as age, gender, health and genetic factors affect the antibody concentration needed to provide protection against the disease. 

It is likely that protection against diseases confined to mucous membranes, such as ear infections, requires a higher antibody concentration compared to coverage against invasive disease.

Reference

1. Käyhty H, Peltola H, Karanko V, Mäkelä PH. The protective level of serum antibodies to the capsular polysaccharide of Haemophilus influenzae type b. J Infect Dis. 1983; 147:1100.