AUTHORS
Rabab Batool, Mohammad Tahir Yousafzai, Fatima Mir, Sajid Muhammad, Saqib Ali Shaikh, Sikander Memon, Farah Naz Qamar
ABSTRACT
Background
This study aimed to assess the longevity of serologic response and seroconversion rates at several time points following TCV vaccination among children living with HIV aged 6 months to 15 years in Pakistan.
Methods
From November 20, 2020, to January 2, 2021; 336 children were enrolled and followed up prospectively for 12 months. Blood samples were collected before the administration of TCV and at 4–6 weeks, 6 months, and 1 year after administration of a single dose (0.5 ml) of intramuscular Typbar TCV®. Samples were analyzed for anti-Vi-IgG antibodies using ELISA. Geometric mean titers (GMTs) and seroconversion rates (fourfold rise in anti-Vi-IgG from baseline) were assessed, and factors associated with sustained seroconversion at 1 year were evaluated using generalized linear mixed models.
Findings
The seroconversion rates were significantly lower in children aged 6 months to 5 years compared to children > 5 years; (127/216 (58·8%)) versus (81/111 (73·0%)) at 6 months and (110/217 (50·7%)) versus (78/109 (71·6%)) at 1 year, only two-third; 188/326 (57·7%) remained seroconverted at 1 year. The GMTs (95 % CI) were significantly lower in children aged 6 months to 5 years compared to children > 5 years, 9·6 (7·6, 12·0) versus 28·9 (20·2, 41·4) at 6 months, and 6·6 (5·4, 8·0) versus 23·1 (16·4, 32·5) at 1 year time point. The odds of sustained seroconversion significantly decreased with time (adjusted odds ratio (aOR): 0.23; 95 % CI: 0.14, 0.40). The odds of sustained seroconversion following 1 year of TCV vaccination were significantly higher among children with non-severe HIV clinical disease (aOR: 10·61; 95% CI: 1·52, 73·98) and children in elder age group (aOR: 7·45; 95% CI: 1·18, 47·03).
Conclusions
A significant decrease in seroconversion rates was observed among children living with HIV following one year of TCV administration. The decline was significantly higher in children with severe or advanced HIV clinical disease and children younger than five years of age.
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