Immunogenicity of alternative and reduced immunization schedules using the thirteen-valent polysaccharide conjugate vaccine against infection with Streptococcus pneumoniae.

In the Netherlands nationwide pneumococcal vaccination was introduced in June 2006, with a 4-dose schedule in which children receive their vaccinations at 2, 3, 4 and 11 months of age. The reduction of the current 4-dose schedule into a 3-dose pneumococcal vaccination schedule would result in a smaller burden for the children. Furthermore, it would also cause an annual reduction of approximately € 8,000,000 in costs for the National Immunization Program (NIP). However, reduction of the vaccination schedule may also require the use of different vaccination moments e.g. at 3 and 5 months of age. There are 2 reasons for this assumption. First, at a later age the immune system of the infant is more developed and this may result in a better immune response. Second, the primary vaccination series are spread more evenly over the time period where protection of the infant is most needed.

There are 3 objectives within this study:

1. Assessing the optimal PCV vaccination schedule: To assess the effect of the use of pneumococcal vaccination schedules with alternative timing and reduction of the number of vaccination doses on the serological response directed against the different serotypes of pneumococci. This information will be used to investigate whether a different timing or reduction of the vaccination schedule will induce antibody responses that are equal to or
better than those obtained by the currently used vaccination schedule. The primairy endpoint for this study will be the antibody titer measured at 12 months, 1 month post-booster.

2. Kinetics of the antibody titer: To assess the kinetics of the pneumococcal antibody titers, in particular in the interval between the last vaccination dose of the primairy series and the booster vaccination at 11 months. This period coincides with the peak incidence of pneumococcal invasive disease and therefore blood samples are taken at 1 month after the primary series (at 5 or 6 or 7 months of age), at 8 months and 11 months.

3. Interference of vaccination with PCV on other vaccinations: To investigate the possible influence of the pneumococcal vaccination on the serological responses of the other vaccine components of the NIP which are administered simultaneously in the other limb (DTaP-IPVHib).

The study population will consist of 4 groups of each 100 children with the following vaccination schedules:

1. PCV13 at 2-3-4-11 months;

2. PCV13 at 2-4-6-11 months;

3. PCV13 at 2-4-11 months;

4. PCV13 at 3-5-11 months.

All children will receive the DTaP-IPV-Hib vaccination according to the NIP at 2-3-4 and 11 months.

Blood samples will be taken at 1 month after the primary series (at 5 or 6 or 7 months of age), at 8 months of age, at the pre-booster moment (11 months) and one month postbooster (12 months).

The groups of children with the 2 + 1 schedule will be offered an extra vaccination at 24 months to complete their series of pneumococcal vaccinations in accordance with the regular NIP.

The vaccination study described here is in full agreement with the advice of the Health Council and also is proactive as it will be performed using the new 13-valent pneumococcal conjugate vaccine (PCV13, Wyeth) instead of the currently used 7-valent vaccine (PCV7, Wyeth).

In the Netherlands nationwide pneumococcal vaccination was introduced in June 2006, with a 4-dose schedule in which children receive their vaccinations at 2, 3, 4 and 11 months of age. The reduction of the current 4-dose schedule into a 3-dose pneumococcal vaccination schedule would result in a smaller burden for the children.
Furthermore, it would also cause an annual reduction of approximately € 8,000,000 in costs for the National Immunization Program (NIP). However, reduction of the vaccination schedule may also require the use of different vaccination moments e.g. at 3 and 5 months of age. There are 2 reasons for this assumption. First, at a later age the immune system of the infant is more developed and this may result in a better immune response. Second, the primary vaccination series are spread more evenly over the time period where protection of the infant is most needed.
The hypothesis is that a different timing and/or reduction of the pneumococcal vaccination schedule will induce antibody responses that are equal to or better than those obtained by the currently used vaccination schedule.

Blood sample time points are:

1. 1 month after the primary series (5 or 6 or 7 months);

2. 8 months;

3. 11 months (pre-booster);

4. 12 months (post-booster).

4 Groups of 100 children:

1. To administer PCV13 at 2-3-4-11 months;

2. To administer PCV13 at 2-4-6-11 months;

3. To administer PCV13 at 2-4-11 months;

4. To administer PCV13 at 3-5-11 months.

All children will receive the DTaP-IPV-Hib vaccination according to the NIP at 2-3-4 and 11 months.

Blood samples will be taken at 1 month after the primary series (at 5 or 6 or 7 months of age), at 8 months of age, at the pre-booster moment (11 months) and one month postbooster (12 months).

The groups of children with the 2 + 1 schedule will be offered an extra vaccination at 24 months to complete their series of pneumococcal vaccinations in accordance with the regular NIP.