Journal of Vaccine Research 2024, Vol.14, No.6, 278-286 http://medscipublisher.com/index.php/jvr 283 In Taiwan, their vaccination program prevented about 4 200 liver cancer cases and saved around $1 billion in healthcare costs over 25 years (Chen et al., 2015). Worldwide, by cutting down the need for liver transplants and expensive medicines, vaccination programs have helped make healthcare systems stronger and less costly. Low- and middle-income countries, which often have more HBV cases, also benefit a lot. Thanks to support from groups like GAVI (the Global Alliance for Vaccines and Immunization), many countries have been able to start HBV vaccination programs. For example, with GAVI's help, vaccination rates in Africa rose to over 80%, leading to big health wins and big savings (Liu et al., 2019). 6 Challenges and Knowledge Gaps Hepatitis B vaccination programs have done a lot of good. But there are still some problems and questions. We still need to find out if booster shots are really needed, if the protection lasts for a very long time, and if vaccines work well against new types of HBV. 6.1 Booster dose necessity There is still no clear answer about booster shots. Most studies say that healthy people who finish their first set of shots stay protected for life, even when their antibody levels go down (Madaliński et al., 2015). But some research shows that people who often get exposed to HBV, like healthcare workers, might need booster shots now and then to stay safe (Lu et al., 2008). Right now, WHO says healthy people don't need booster shots. But experts are still talking about whether special groups should get extra doses (Chlibek et al., 2011). 6.2 Gaps in longitudinal data Another big problem is that we don't have enough long-term studies. We know protection usually lasts 20~30 years after getting the shots, but we are not sure what happens after that (Gilca et al., 2013). Many studies don't follow kids who were vaccinated as babies all the way into adulthood, especially in poorer countries. This makes it hard to know exactly how long the vaccine keeps working. In places where HBV is common, people may naturally get exposed to the virus again. This can boost their immune system without them knowing. That makes it even harder to figure out how much of their protection comes just from the vaccine (Simons et al., 2016). Setting up programs to follow people for many years and collect good data would help solve this problem. 6.3 Emerging variants and vaccine effectiveness HBV is a virus that can change over time. Some new types, called "vaccine-escape variants," have already been found. These new types show up more often in places where lots of people have been vaccinated (Kao, 2015). This has made some experts worry that the vaccines we use today might not work as well in the future. For now, the vaccines we have still work very well. But if more new virus types show up, we might need to make new vaccines or find other ways to stay protected (Flores et al., 2022). That's why it's really important to keep checking HBV strains around the world. We need to catch any changes early before they become a big problem. 7 Future Directions 7.1 Development of next-generation vaccines Scientists are working on new vaccines to fix the problems with the ones we have now, especially to deal with new types of HBV. The new vaccines might target more parts of the virus, like the core antigen. This could help stop virus types that the current vaccines can't fully cover (Flores et al., 2022). They are also trying new adjuvants —special ingredients that help vaccines work better. These could help people like older adults and those with weak immune systems get stronger protection (Kao, 2015). Some new vaccines are being made with DNA or mRNA technology. These might last longer and cut down the need for booster shots (Simons et al., 2016). 7.2 Improved monitoring and surveillance systems We need better systems to track how well HBV vaccination programs are working over time. Stronger national and global databases could help us see how long antibodies last, how good immune memory is, and how often people still get infected after vaccination (Razavi-Shearer et al., 2018). If we also track different types of HBV, we can spot new virus types early and update vaccines when needed (Launay et al., 2016). It's also important to keep
RkJQdWJsaXNoZXIy MjQ4ODYzNQ==