Intention to vaccinate and vaccination behaviour of parents with regard to hepatitis B vaccination of their child

Discrete choice experiments (DCE) are increasingly used in the field of health
economics to study choice preferences of individuals. A critique on DCEs is
that its* external validity may be restricted since results are limited to
stated (hypothetical / without burden) preferences while actual behavior may
differ from stated preferences. As very little research has been conducted on
this potential methodological pitfall in DCEs, this study aims to link the
stated preferences of young parents for hepatitis B vaccination of their
newborn child with their actual vaccinating behavior.

In the first phase of this study a DCE-questionnaire was distributed among 2000
parents, who gave birth to a child in the previous two weeks. The questionnaire
was distributed on March 23, 2011. These parents were asked to study four
choice situations each containing two scenarios. For each of the four choice
situations, parents were then asked to indicate in which scenario they were
more likely to vaccinate their child against hepatitis B. The scenarios
contained items on; the information about the protection of the vaccine; risk
of side effects; manner of vaccination (single vaccination or part of
cocktail); information from formal institutions emphasizing safety (GP, infant
welfare centre, national health authority); information from other (informal)
sources emphasizing risks (TV, social media, friend); and social context (all
friends vaccinate their children versus none of the friends and relatives
vaccinate their children).
An accompanying questionnaire measured the DCE scenario items on the individual
level. This included questions on the respondents* estimation of the protection
of the vaccine, side effects, opinion on manner of vaccination, their use of
formal sources for information, their use of informal sources for information
and vaccination behavior of their friends.

In the second phase of this study, parents* actual behavior with regard to
acceptance of hepatitis B vaccine will be tested. In order to do that, the
parents who returned the questionnaire and indicated that they are willing to
participate in further research will be offered to vaccinate their child
against hepatitis B. Parents are free to either accept or reject this
vaccination offer. Their response and the concordance between their answers to
the questionnaire as distributed in phase 1 of the study and acceptance of
vaccination will be the subject of phase 2 of our study.

The primary aim of our study is to link stated preferences of parents of
newborn children for hepatitis B vaccination to actual vaccination behaviour.
The secondary objective is to determine the external validity of the Discrete
Choice Experiment as used in phase one of the study as a tool for predicting
people*s behavior and to study the association of background characteristics of
parents with the agreement (if any) between hypothetical preferences (choices
made in the Discrete Choice Experiment) and revealed preferences (actual
vaccination behaviour).

This study is an observational study including parents of newborn children who
indicated that they were willing to participate in further research. This study
only includes subjects from a previous questionnaire-based study (protocol
number 11-069/C). Within the current study parents are given the opportunity to
have their child vaccinated with a vaccine that has a hepatitis B component in
addition to the regular vaccination components (diphtheria, tetanus, pertussis,
poliovirus and Haemophilus influenzae type b) that every child in the
Netherlands is offered within the context of the National Immunisation Program.
This study does require that parents provide information on whether or not
they have their child vaccinated with a vaccine including hepatitis B or with
the regular vaccine (without hepatitis B) only.

There is no additional burden for parents to participate in this phase of the
study (except returning the answering card including informed consent).
Children will receive a 6-valent vaccine instead of a 5-valent vaccine, but no
additional adverse events are expected to occurr with this vaccine. The vaccine
has been used (since 2003) in the National Immunisation Programme for over
300,000 newborns (born in families with at least one parent from a hepatitis B
endemic country) without any major problems. The 6-valent vaccine will bring
the child additional protection to hepatitis B infection, compared to the
5-valent vaccine.