Journal of Tropical Pediatrics Advance Access published online on November 4, 2009
Journal of Tropical Pediatrics, doi:10.1093/tropej/fmp104
Effect of Season of Inoculation on Immune Response to Rubella Vaccine in Children
aDepartment of Neonatology, Rabin Medical Center, Schneider Children's Medical Center of Israel, Petach Tikva, Israel
bSackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
cCentral Virology Laboratory of the Ministry of Health, Chaim Sheba Medical Center, Tel Hashomer, Israel
dDepartment of Mother, Child and Adolescent Health, Ministry of Health, Jerusalem, Israel
eThe Johns Hopkins University, Baltimore, MD, USA
fPediatric Infectious Disease Unit, Schneider Children's Medical Center of Israel, Petach Tikva, Israel
Correspondence: Prof. N. Linder, Department of Neonatology, Rabin Medical Center, 2, Denmark Str., Petach Tikva 49100, Israel. Tel.: +972-3-937-7474; Fax: +972-3-937-7469. E-mail <linderm{at}netvision.net.il>.
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Abstract |
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The yearly seasons are marked by changes in the amount of sunlight. Ultraviolet radiation (UVR) is known to adversely affect the course of viral infections, immunologic memory and cellular and humoral immune responses. Our objectives were to investigate potential differences in the immune response of the rubella vaccine after 3–4 years by season of inoculation. Children aged 4–5 years attending four kindergartens in villages in northern Israel, all of whom had been vaccinated at 1 year of age, were enrolled in the study. Participants were divided into three groups by season of the year in which the inoculation was performed: summer (N = 63), winter (N = 36) and intermediate (N = 104). Main outcome measures were mean geometrical titer of rubella antibodies and complete, partial or no immunity to rubella by season of inoculation. Of the 203 children tested, 186 (91.6%) had adequate antibody levels, 7 (3.4%) had equivocal levels and 10 (4.9%) had inadequate levels. Significantly higher mean geometrical titers were found in the winter-inoculated compared with the summer-inoculated group (73.0 ± 2.6 vs 47.6 ± 2.8; p < 0.05). The same tendency was noted in the percent of infants properly immunized. This preliminary study shows a strong correlation between the immune response to rubella vaccine and the season of vaccination. Immunogenicity may be improved by inoculating children during seasons of less sunlight or by reducing the children's exposure to sunlight following inoculation. This practice is especially important in areas with extreme seasonal variability in solar radiation and tropical areas. Further studies are needed to corroborate and expand these findings.