Introduction:
Pneumococcus is a common organism causing invasive
bacterial disease, especially in children < 2 years and elderly
adults. Pneumococcus has more than 90 subtypes. Of these, 10 subtypes
cause > 90% of childhood infection.
Disease
spectrum: Pneumococcus can lead to invasive diseases
like sepsis, meningitis, pneumonia and local infections like ear
infection (otitis media), cellulitis, arthritis, etc. The peak incidence
of pneumococcal disease is at 6-24 months of age.
It is estimated that in USA, annually pneumococcus leads to 3000
cases of meningitis, 50,000 cases of sepsis, 500,000 cases of pneumonia
and 7 million cases of ear infection with 40,000 deaths.
There are now vaccines available to prevent infection by
some of the common subtypes of pneumoccocal bacteria.
-
Unconjugated Pneumococcal Vaccines:
It is active against 23 subtypes of pneumococcus.
It is available since several decades. The action is short lived
and cannot be used below 2 years of age when it is most required.
At best it has efficacy of 70% in healthy adults against invasive
disease and only 56% in those > 65 years of age. It is given
in children above 2 years of age with sickle cell anemia, splenectomised
patients and in patients with low immunity.
-
Conjugated Pneumococcal Vaccine:
Vaccines against 7, 9 and 11 subtypes have been tried and of this
7 valent conjugated vaccine (Prevenar) is commercially available.
Schedule:
Children presenting before 7 months of age are given 3 primary doses
at 2,4 & 6 months or 2,3,4 months or at 6,10,14 weeks depending
on local schedule, & a booster at 12-15 months. Children coming
between 7-12 months are given 2 primary doses at 4-8 weeks interval
& booster at 12-15 months. Children presenting between 12-24
months are given 2 doses at 4-8 weeks interval & those coming
after 24 months till 5 years of age are given a single dose of the
vaccine. It is given intramuscularly over the arm of the thigh.
Complication: 7-valent
conjugate vaccine given to infants is a very safe vaccine. Mild
local reactions are seen in 30-35% of patients and include redness,
warmth, pain, and tenderness. Fever of 38-39 degree C is seen in
25-30% of recipients.
Limitations:
The cost at the moment is very high.
