A parallel-group, randomized, open-label study will be performed in subjects receiving PCV7 and subjects receiving controlled vaccine Hib vaccine, to claim the efficacy of PCV7 in the prevention of NP carriage of vaccine-serotype S. pneumoniae (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F combined) in 2 to 5 years old healthy Chinese children.

In 2005, clinical trials with PCV7 (Prevenar) were first conducted in China. In the phase 3 study involving Chinese infants, Prevenar was shown to be immunogenic, well tolerated, and safe when given either separately or concomitantly with a diphtheria, tetanus, and acellular pertussis (DTaP) vaccine at 3, 4, and 5 months of age. Controlled clinical trials elsewhere in the world showed the correlation between immunogenicity and disease prevention. In addition to the direct effect of Prevenar, immunization of children has also reduced the incidence of disease in adults. The changes are presumed to be due to reductions in nasopharyngeal carriage of vaccine serotype S. pneumoniae in children who have been vaccinated.

The purpose of this study will be to assess the effectiveness of Prevenar vaccination to reduce vaccine serotype (VT) NPC rates in Chinese children aged 2 to 5 years old.

Inclusion Criteria:

1. Healthy children aged 2 to 5 years.
2. Evidence of a personally signed and dated informed consent document indicating that the parent(s) (or legal guardian) has been informed of all pertinent aspects of the study.
3. Subjects and parents / legal guardian/ adult caregiver who are willing and able to comply with scheduled visits, treatment plan, and other study procedures.
4. Available for entire study period and whose parent/legal guardian/adult caregiver can be reached by telephone.
5. Healthy child as determined by medical history, physical examination, and judgment of the investigator.

Exclusion Criteria:

1. Previous vaccination with licensed or investigational pneumococcal vaccine.
2. Receipt of a full series or catch-up dose of licensed or investigational Hib vaccinations.
3. Contraindication to vaccination with a pneumococcal conjugate vaccine or Hib.
4. Bleeding diathesis or condition associated with prolonged bleeding time that would contraindicate intramuscular injection.
5. Known or suspected immune deficiency or suppression including treatment with systemic steroids, anti-metabolites, chemotherapy and immunomodulatory agents.
6. Major known congenital malformation or serious chronic disorder.
7. Malformation or injury of the nasopharynx that makes the procedure of taking a nasopharyngeal swab impossible.
8. Significant neurologic disorder including congenital neurological disease in sibling of the subject or history of seizure including febrile seizure, or significant stable or evolving disorder such as cerebral palsy, encephalopathy, hydrocephalus, or other significant disorder. Does not include resolving syndromes due to birth trauma such as Erb's palsy.
9. Receipt of blood products or gamma-globulin (including hepatitis B immunoglobulin and monoclonal antibodies) within 12 weeks prior to enrollment.
10. Participation in another investigational or interventional trial within the 28-day period before enrollment and during the conduct of the study. Participation in purely observational studies is acceptable.
11. Subjects whose parents or legal representative are investigational site staff members or subjects whose parents or legal representative are Pfizer employees directly involved in the conduct of the trial.

Temporary Exclusion Criteria(The following conditions are temporary or self-limiting and a subject may be included in the study once the condition(s) has/have resolved and no other exclusion criteria are met):

1. Subjects with current febrile illness (axillary temperature of ≥ 38.0ºC).
2. Subjects who used antibiotics within the previous 15 days.