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Typhim Vi vaccine against typhoid fever: a clinical trial in Kenya
N B Mirza1, I A Wamola, B A Estambale
1Department of Medical Microbiology, University of Nairobi, Kenya.
Insights
The purified Vi polysaccharide vaccine (Typhim Vi) is safe and effective for preventing typhoid fever in children. Vaccination demonstrated high seroconversion and seroprotection rates with minimal, transient side effects.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Typhoid fever remains a significant public health concern, particularly in endemic regions.
- Effective vaccines are crucial for controlling its spread, especially in pediatric populations.
Purpose of the Study:
- To assess the safety, tolerance, and immunogenicity of the purified Vi polysaccharide vaccine (Typhim Vi) in primary school children.
- To determine seroconversion and seroprotection rates following vaccination.
Main Methods:
- A total of 435 children aged 5-15 years received a single intramuscular dose of Typhim Vi.
- Vi antibody levels were measured using Radioimmunoassay (RIA) on paired sera from 110 children before and 30 days after vaccination.
Main Results:
- A seroconversion rate of 76.2% was observed, with a post-vaccination seroprotection rate of 74.2%.
- Pre-existing protective immunity was noted in 6.2% of children.
- The vaccine was well-tolerated, with most common reactions being mild injection site pain (83%) and infrequent mild swelling, induration, itching, or headaches, all resolving within 48 hours.
Conclusions:
- The purified Vi polysaccharide vaccine (Typhim Vi) is safe and elicits a robust immune response in primary school children.
- The vaccine is a viable option for typhoid fever prevention in this age group, demonstrating good tolerance and efficacy.
Abstract:
Safety, tolerance and immunogenicity of the purified Vi polysaccharide vaccine (Typhim Vi) against typhoid fever was evaluated in primary school children aged 5-15 years. A total of 435 children were vaccinated, each with a single intramuscular injection in the left deltoid muscle. One hundred and ten children were randomly selected for blood samples on day 0 (pre vaccination) and day 30 (post vaccination). Vi antibodies studied by Radio immuno assay (RIA) on 97(88%) paired sera showed a seroconversion rate of 76.2% and seroprotection rate after vaccination was 74.2%, while 6.2% of children already had protective immunity before vaccination. The vaccine was well tolerated. Most commonly reported reactions were mild pain at site of injection (83%), and a few complained of mild swelling (4.6%), induration (1.1%), itching (1.1%) and headaches (1.4%). All reactions were of mild severity and disappeared within 24 to 48 hours.