• To address the most common cause of enteric fever, a study was conducted to assess the safety and immunogenicity of a new bivalent paratyphoid A- typhoid conjugate vaccine (Sii- PTCV).

• The study was a phase 1, double-blind study among 60 participants, who were randomized into 2 groups.

• The intervention group received a single intramuscular injection of Sii-PTCV, whereas the control group received a single intramuscular injection of Typbar TCV.

• The safety of the intervention was assessed at 1 week, 1 month, and 6 months.

• The immunogenicity was assessed at 1 month and 6 months using the following:

1. Against typhoid: Anti-capsular polysaccharide antigen Vi (anti-Vi) IgG and IgA.

2. Against paratyphoid A: Anti-lipopolysaccharide (LPS) IgG and functional antibody.

• The most common solicited side effects were pain and myalgia, which were comparable among the two groups.

• The study did not report any unsolicited adverse events.

• The two vaccines had comparable immunogenicity against typhoid, whereas Sii-PTCV showed 100% seroconversion for anti-LPS IgG at day 29.

• However, further trials are needed to strengthen the evidence.

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