Effect of Zinc Supplementation on Response to Oral Polio Vaccine in Infants in Pakistan
Status:
Completed
Trial end date:
2011-01-01
Target enrollment:
Participant gender:
Summary
Pakistan is one of the 4 developing countries where cases of poliomyelitis are still being
identified. Despite the incessant efforts by WHO and UNICEF, this disease is far from
control. There is a need to develop new and innovative strategies to contain the disease and
eradicate it from the countries where new cases continue to be identified.
Zinc is an essential component of scores of enzymes in the human body. Recent reports have
indicated that this trace element along with other micronutrients enhances the protective
functions of immune cells. Moreover, zinc deficiency leads to dysregulation of balanced host
responses to infection resulting into decreased antibody production and suppressed immunity.
Zinc is also an essential cofactor for thymulin which is known to modulate cytokine release
and induce immune cell proliferation. Zinc deficiency is also found to impair an individual's
epithelial barrier function, which may further depress the vaccine entry into the mucosal
cells.
Role of zinc in the prevention of diarrheal diseases and other infections in children is well
documented. However, there are very few reports about its contribution to enhanced immunity
by supporting body's natural defense system.
Zinc insufficiency is widespread in socioeconomically deprived children in South Asia and the
recent most national nutrition survey (2003) . Moreover, diarrhea is also very common in
infants in Pakistan. Such diarrheal episodes can limit entry of attenuated polio virus into
the mucosal cells, thereby, leading to inadequate immune response. Association between recent
diarrheal history and increased vaccine failure in infants has been shown in a study from
Brazil. The recent Lancet Nutrition series has also recommended regular zinc supplementation
to address child undernutrition and stunting and underscored the need to treat diarrheal
episodes with zinc to expedite recovery. Other recent studies of zinc supplementation in low
birth weight infants in South Asia have also shown significant improvement in diarrheal
disease burden and mortality.
On the basis of these lines of evidence, it is possible that some of the cases of vaccine
failure in this region could be a consequence of compromised immunity and, hence, diminished
response to OPV. This could potentially be reversed by addressing such gross undernutrition
and micronutrient deficiencies. It can thus be hypothesized that zinc supplementation at
community scale would enhance the immune response in infants to OPV.
In order to test this research question, the investigators propose to undertake 12-month
randomized controlled trial among a cohort of Pakistani infants of 0-14 days of age. Such a
trial would enable us to understand the synergistic role of zinc (if any) with OPV in
enhancing immune response against polio and sero-conversion rates.