Journal of Vaccine Research 2024, Vol.14, No.6, 278-286 http://medscipublisher.com/index.php/jvr 281 4.1 Vaccine dosage and schedule The amount of vaccine and the timing of the shots are really important. The usual three-shot plan (at 0, 1, and 6 months) works well for most healthy kids and adults. Over 90% of them become protected (Marshall et al., 2010). But sometimes, people follow different plans: 1) Fast Schedules: Travelers and people who need quick protection get shots at 0, 7, and 21 days, plus a booster at 12 months. This gives fast protection, but the antibody levels drop faster than with the regular plan (Launay et al., 2016). For example, healthcare workers who used the fast schedule needed extra booster shots after 5~7 years. Figure 2 shows that different people might need different vaccine plans. Figure 2 Recommended hepatitis B virus vaccination schemes (Adpoted from Di Lello et al., 2022) Image caption: The hepatitis B immunization schedule is flexible, but minimal intervals and ages need to be observed. The recommended dose varies (5~40 μg of hepatitis B surface antigen protein/mL) depending on the individuals’ age and the vaccine brand. aMonovalent hepatitis B vaccine 0.5 mL must be used for the at birth immunization (HepB-BD). Immunocompromised adults or patients under dialysis require larger or additional doses of the hepatitis B vaccine; bCombined hepatitis B, diphtheria, tetanus, adsorbed acellular pertussis, inactivated poliovirus vaccine. This vaccine cannot be administered at birth, before 6 postnatal weeks, or at age ≥ 7 years; cHeplisav-B is a vaccine recently approved for adults; it has a novel adjuvant and its recommended schedule is two doses 1 mo apart. HepB3: Three doses of hepatitis B vaccine; HepB-BD: Monovalent single dose of the hepatitis B virus vaccine; HBIG: Hepatitis B Immunoglobulin (Adpoted from Di Lello et al., 2022) 2) Low-Dose Vaccines: Pediatric doses are effective in generating initial immunity but may result in lower long-term antibody persistence. In one study, children vaccinated at birth showed a 40~60% decline in protective anti-HBs levels by adolescence (Gilca et al., 2013). 3) Booster Shots: Some groups, like healthcare workers or people living where HBV is common, often need booster shots later. A study in Taiwan showed that giving a booster 10~15 years after the first shots helped more than 90% of people get back their protection (Wu et al., 2011). 4.2 Individual variability in response Not everyone's body reacts the same after getting the vaccine. Some people naturally build stronger protection than others. 1) Genes: About 5~10% of people don't respond well because of their genes. These "non-responders" don't make enough antibodies after their shots (Simons et al., 2016). 2) Age at Vaccination: Babies who get vaccinated at birth lose their antibodies faster than kids or adults who get vaccinated later. One study found that by age 15, about 50% of kids vaccinated as newborns lost their antibodies, compared to 30% of kids vaccinated at 5 years old (Lu et al., 2008). 3) Health and Habits: Things like diabetes, smoking, or being overweight can make the vaccine work less well. For example, people with diabetes had 20~30% lower protection rates than healthy people in several studies (Buti et al., 1992).
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