Typhoid fever, a life-threatening bacterial infection caused by the bacterium Salmonella Typhi, remains a significant public health issue globally, especially in developing regions lacking access to clean water and sanitation.
In India as well typhoid fever remains an important public health challenge that disproportionately impacts children.
Typbar Typhoid Conjugate Vaccine (TCV)ย was developed by Hyderabad-based Bharat Biotech which is the world’s first clinically proven conjugate vaccine offering long-term protection against typhoid.
Typbar Typhoid Vaccine
The Typbar vaccine is a well-known vaccine used to prevent typhoid fever, a serious and potentially fatal disease caused by the bacterium Salmonella Typhi. The Typbar vaccine is significant in public health efforts, especially in endemic regions, as it helps reduce the incidence of this disease.
Typbar is available in two main forms:
- Typbar TCV (Typhoid Conjugate Vaccine): This is a more recent and advanced version, suitable for children as young as six months of age, and provides longer-lasting immunity than the older polysaccharide vaccines. It is a conjugate vaccine, which means that the polysaccharide antigen is chemically linked to a carrier protein, enhancing the immune system’s response to the vaccine.
- Typbar Vi Polysaccharide Vaccine: This is an older version of the typhoid vaccine, suitable for children over two years of age and adults. It offers good protection but needs to be administered more frequently than the TCV for sustained immunity.
Efficacy and Duration:
- Typbar TCV: Studies have shown that the Typbar TCV is highly effective in preventing typhoid fever, with a single dose providing long-lasting protection. The World Health Organization (WHO) has recommended the Typbar TCV for routine immunization programs, especially in countries with high typhoid prevalence. The protection duration is believed to be at least 5 years, with ongoing studies to determine the exact duration of immunity.
- Typbar Vi Polysaccharide Vaccine: While effective, the immunity from the polysaccharide vaccine tends to wane after 2 to 3 years, necessitating booster doses for continued protection.
Administration:
The Typbar vaccine is administered as an injection. The TCV is usually given as a single dose, which can simplify vaccination campaigns and ensure broader coverage in endemic areas.
Safety and Side Effects:
The Typbar vaccine is generally safe and well-tolerated. Common side effects are mild and may include pain at the injection site, fever, headache, and nausea. These side effects typically resolve without treatment within a few days.
What is a Conjugate Vaccine?
Typbar TCV is a conjugate vaccine.
Conjugate vaccines combine a weak antigen with a strong antigen or carrier protein. This augments the immune response to the weak antigen, creating a more robust and durable immune response.
For Typbar, the weak S. Typhi antigen is conjugated with a carrier protein. When injected, this triggers the body to produce T-cell-dependent anti-S. Typhi antibodies and memory B cells.
The carrier protein enables the induction of immune memory, providing long-lasting immunity against typhoid fever.
Also read: Immunity: Understand Human Immune System
Significance of Typbar Typhoid Vaccine
The significance of the Typbar Typhoid Vaccine is:
- The results so far demonstrate Typbar TCVโs ability to provide durable, long-term protection against typhoid fever in both children and adults.
- It is the first typhoid vaccine to show efficacy beyond 2 years post-vaccination.
- Earlier efficacy trials had follow-up periods of only 2-3 years after vaccination.
- The 4-year protection data is vital evidence for policymakers considering large-scale typhoid vaccination.
- The findings validate Typbar TCVโs role in long-term typhoid control and prevention in endemic regions.
Typhoid Disease Burden
Typhoid remains a serious public health problem that disproportionately impacts children and marginalized populations in Asia and Sub-Saharan Africa lacking access to safe water and sanitation.
- In 2019, nearly 11 million typhoid cases and 110,000 typhoid deaths occurred globally.
- Children bear the highest burden, with the majority of cases and deaths occurring in children under 15 years of age.
- South Asia accounts for nearly 80% of the global typhoid burden, followed by Sub-Saharan Africa.
- Antimicrobial resistance is making typhoid harder to treat, increasing risks of complications and death.
- Outbreaks continue to emerge globally, including in Fiji, Pakistan, and the Democratic Republic of Congo in recent years.
- Climate change and increasing urbanization may further increase typhoid risk in vulnerable regions.
Also Read: Sanitation System in India
Role of Vaccination
The role of vaccination for typhoid is:
- Typhoid vaccination is an important prevention strategy, alongside safe water, sanitation, and hygiene interventions.
- Multiple typhoid vaccines exist, but Typbar TCV is the only one suitable for children under 2 years old.
- Its compatibility with routine childhood immunization schedules facilitates reaching high coverage.
- WHO recommends routine programmatic use of TCVs in typhoid-endemic countries.
- Gavi provides financial support for vaccine introduction in eligible low-income countries.
- Over 20 countries have introduced TCVs so far, including Nepal, Bangladesh, Pakistan, Liberia, Zimbabwe, and India.
- Widespread TCV vaccination can significantly reduce disease incidence and save lives.
Why in the news?
Recently, a phase-3 clinical trial conducted in Malawi, Africa has demonstrated the long-term protective efficacy of Bharat Biotech’s Typbar Typhoid Conjugate Vaccine (TCV) in children and adults.
These landmark findings have vital implications for India’s typhoid control strategy.
The trial provides the first evidence of long-term efficacy for TCVs in children aged 9 months to 12 years.
- Typbar TCV conferred 77% protective efficacy against typhoid fever through 4 years post-vaccination.
- The efficacy was consistent across all age groups studied, including infants, toddlers, young children, and older children.
- Typbar is the worldโs first clinically proven conjugate typhoid vaccine with long-term protection data.
- The results validate Typbar TCV as a tool to improve long-term typhoid fever control in endemic regions.
Trial Design of Typbar Typhoid Vaccine
Phase 3, a double-blind, randomized, controlled field trial was conducted from 2015 to 2019 in Blantyre, Malawi. This urban area has a high burden of typhoid.
The trial had over 20,000 participants aged between 9 months and 45 years. They were randomized to receive either a single dose of Typbar TCV or a control vaccine.
Blood samples were collected and tested for anti-S. Typhi antibodies periodically after vaccination. Participants were followed for typhoid fever incidence through passive surveillance at health centers.
Key Findings
Some important findings related to the Typbar Typhoid Vaccine are:
- From 9 months to 4 years post-vaccination, the cumulative efficacy of Typbar was 77%.
- Protection was consistent across all pediatric age cohorts – infants, toddlers, young children, and older children.
- Seroconversion rates (antibody response) exceeded 90% in all age groups.
- No significant waning in antibody titers occurred during the 4 years, indicating sustained vaccine effectiveness.
- The vaccine was well-tolerated with no serious adverse events reported.
The Way Forward
The Malawi trial results validate Typbar TCV as an effective, practical tool for long-term typhoid control even in very young children.
Policymakers in typhoid-endemic countries should utilize these findings to make evidence-based decisions on national typhoid vaccination policies and strategies.
Financial and technical support from partners like Gavi must continue to expedite TCV rollout in countries that need them most.
Investing in typhoid vaccines today will ultimately help save lives, reduce poverty, unlock human potential, and accelerate progress towards the UN Sustainable Development Goals.
Conclusion
The proven long-term efficacy of Typbar TCV is a game-changer for typhoid control in India.
Widespread TCV vaccination, as recommended by WHO, combined with continued investments in water, sanitation, and hygiene, will be pivotal for India to achieve its target of typhoid elimination by 2030 in line with the Sustainable Development Goals.
On the self-reliance front, Typbar demonstrates India’s growing capabilities in developing and producing life-saving vaccines domestically.
Read: Modern vaccines: Why do they have low durability?
Article Written By: Priti Raj
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