Hepatitis B Vaccines

The Institute of Child Health immunization clinic offers services to inhabitants of Benin city, the capital of Edo state in mid-western Nigeria. The services offered include immunization, growth monitoring, nutrition education, and general health education. Immunizations are offered everyday, except for BCG and measles, which are offered only on Fridays. Every child who commences immunization in this facility has a record of his/her biodata and the date of receipt of various vaccines. About 1,000 children per year receive their immunizations in this facility. The immunization services offered were evaluated in terms of the timeliness of receipt of vaccines, the immunization rates for individual vaccines, including the recent additions to the schedule, and the completion rates of the infant immunization schedules
The study included 512 consecutive children who received their routine immunizations at the facility during September 2004–March 2005. Data on date of birth, age at commencement of immunization, place of birth, age of mother, age of father, and the date of receipt of various vaccines were retrieved from the clinic records of these children. Age at receipt of immunization was calculated in days using the dates of birth and the dates of receipt of vaccines. At the time of review of data (March 2007), the youngest child was aged at least 24 months. The number of visits made was also recorded. The uptake of vaccines was recorded as simple percentages.
The timeliness of receipt of a vaccine is determined by the recommended age for receipt of the given vaccine. Previous studies on timeliness, involving schedules recommending receipt of vaccines at specific dates, have allowed 14, 28, and 30 days of the grace period (2 (link),3 ,7 ). In this study, four timeframes were used for evaluating the timeliness of receipt of three doses of oral polio vaccine (OPV1, OPV2, and OPV3), three doses of diphtheria, pertussis and tetanus vaccine (DPT1, DPT2, and DPT3), and three doses of hepatitis B vaccine (HepB birth, HepB2, and HepB3) as follows: (a) too early if the vaccine was received earlier than the recommended age; (b) being on time if the vaccine was received on or before two weeks after the due date; (c) acceptably early if received between two and four weeks after the due date, and (d) delayed if received after four weeks of the due date.
Full immunization was defined as receipt of BCG, three doses of OPV, three doses of DPT, three doses of hepatitis B vaccine, and a dose each of measles and yellow fever vaccines respectively.
Drop-out rate was calculated as the difference in percentage coverage in between the consecutive vaccines.

Between October 2016 and October 2018, HIV–negative women were recruited from Cape Town and Johannesburg, South Africa, and Harare, Zimbabwe (ClinicalTrials.gov NCT02732730). Women were eligible if they were literate, female at birth, ages 16 to 25 years, had vaginal or anal sex in the month prior to screening, and reported interest in taking PrEP in the 36-item HIV Prevention Readiness Measure about risk behaviors, medical care utilization, and PrEP beliefs (adapted from the HIV Treatment Readiness Measure) [15 (link)]. To screen out lower risk women, we required a VOICE rick score ≥5, which was associated with >6% HIV incidence in prior cohorts [16 (link)]. In addition, women needed to have regular access to a mobile phone with SMS capacity, be hepatitis B seronegative, and willing to accept hepatitis B virus (HBV) vaccine (if previous immunity was not confirmed), have normal renal function (creatinine clearance >60 ml/min), and not be pregnant. Study visits were at months 1, 2, 3, 6, 9, and 12 with HIV and pregnancy testing at every visit (S1 Text).

The cross-sectional study was conducted from July to December 2019 and the cohort from January to May 2020. In phase I, CHWs aged 18 years or older were included and those who were on vacation and/or leave on the scheduled dates were excluded. Therefore, of the 172 CHWs, 36 were on vacation or leave and were excluded from the study. The inclusion criteria for the cohort (phase II) were: CHWs who had three doses of the hepatitis B vaccine and anti-HBs titers <10 mIU/mL in the serological test. Individuals in this situation were eligible to receive the challenge dose¹².

Initially, a virtual invitation was made by the managers of each unit to the active CHWs. Those who showed up at the scheduled date and place and agreed to participate in the study, after signing the Free and Informed Consent Term (FICT), were invited to answer the questionnaire. This questionnarie contained questions about socio-demographic characteristics and knowledge about hepatitis B vaccination. After this step, the vaccination card was requested to check the hepatitis B vaccination record; in its absence, information was sought in the National Immunization Program Information System (NIPIS).
Finally, 8 milliliters (mL) of blood sample were collected through venipuncture in the upper limb for hepatitis B serology. All samples were tested for the following serological markers: hepatitis B surface antigen (HBsAg), antibodies to hepatitis B virus core protein (anti-HBc) and anti-HBs. Rapid Test from Bioclin, Brazil, was used for detecting HBsAg marker. The anti-HBc and anti-HBs markers were tested using the chemiluminescence method (Architect i1000TM, Abbott Diagnostics).
The test results were personally delivered to each CHW. Those who were not vaccinated or had an incomplete schedule were oriented to take a new three-dose schedule or to complete the schedule^12,16.
Subjects eligible for phase II received one dose of hepatitis B vaccine (“challenge dose”), conceptualized as administration of one dose of hepatitis B vaccine to screen for the presence of memory antibodies against possible exposure to the virus²⁴. Thus, within 30 to 60 days after vaccination, a new blood sample was collected for serological testing for the anti-HBs marker. The test was performed using the electrochemiluminescence method (Cobas e 411TM, Elecsys Anti-HBs kit, Roche). Individuals who did not present protective anti-HBs titers were referred to the public health care network and oriented to continue hepatitis B vaccination.