An uncertain hepatitis B vaccine history does not, by itself, mean give hepatitis B immune globulin (HBIG). In a sexual-assault evaluation, choose prophylaxis using two separate facts: what is known about the survivor’s vaccination and response, and whether the assailant is known to be hepatitis B surface antigen (HBsAg)-positive. If the survivor has no reliable record of a completed series and the assailant’s status is unknown, give hepatitis B vaccine at the initial visit; the CDC sexual-assault pathway does not add HBIG solely because the source is unknown.
Keep the two decision variables separate
The vaccine prompts the survivor to develop active immunity, which takes time and requires completing the series. HBIG provides passive antibody. When the source is known to be infected and the survivor is susceptible, using both addresses the exposure promptly while vaccination builds longer-term protection.
That mechanism helps prevent a common error: treating unknown source status as equivalent to a confirmed positive result. The CDC’s nonoccupational post-exposure pathway has a distinct branch for an unknown source.
| Assailant’s HBsAg status | Survivor’s documented status | Usual action |
|---|---|---|
| Unknown | No reliable record of a completed vaccine series | Start hepatitis B vaccine now; HBIG is not routinely added for an unknown source. |
| Known positive | Unvaccinated or series incomplete | Give hepatitis B vaccine and HBIG; continue the vaccine series. |
| Known positive | Completed series with documented vaccine response | No additional hepatitis B post-exposure prophylaxis is generally needed. |
| Either status | Completed series, but no post-vaccination response testing | The CDC sexual-assault guidance recommends a single vaccine booster dose. |
A documented prior nonresponse is a separate branch, not the same as a completed series without post-vaccination testing. Use the nonresponder-specific post-exposure pathway based on the source status and vaccination-response history rather than assuming the survivor is protected.
For an uncertain history, act while checking records
Ask whether the patient recalls receiving any doses, where they may have been given, and whether there is a vaccine card, registry entry, or medical record to confirm them. If a complete series cannot be reliably established during the visit, manage the patient as unvaccinated or incompletely vaccinated for this decision and give the first indicated dose. Record retrieval can continue in parallel; it should not postpone time-sensitive prophylaxis.
A baseline blood sample for hepatitis B infection testing is part of the broader post-assault evaluation. But testing for infection and documenting vaccine-induced protection answer different questions. Do not wait for serology to decide whether to begin vaccination when the history is unknown.
If the series was started but not completed, arrange the remaining doses using the schedule for the vaccine product selected. Do not let a missed appointment or uncertainty about the exact prior dates become a reason to abandon follow-up; verify which doses count and make a specific plan to complete the series. The CDC sexual-assault guidance describes follow-up doses at 1–2 and 4–6 months for its three-dose schedule.
Timing, pregnancy, and the handoff
Give indicated prophylaxis as soon as possible, preferably at the initial examination. Post-exposure guidance notes that evidence about the latest effective time is limited; benefit is unlikely to extend beyond about 14 days after sexual exposure. That estimate is not a reason to wait. If presentation is delayed, assess the timing and exposure and consult the relevant local protocol rather than treating the estimate as a guaranteed cutoff.
Pregnancy is not a reason to withhold indicated hepatitis B vaccination. For an obstetric team, this matters because concerns about fetal exposure can otherwise delay a preventive intervention. Use an appropriate vaccine and product-specific schedule, and explain the purpose of each injection in clear, trauma-informed language.
The handoff is part of the prophylaxis plan. Before the patient leaves, document the source-status branch, the vaccine history available, what was administered, and when the next dose is due. Offer a practical way to reconnect for follow-up, especially when the patient may be moving, changing contact information, or facing barriers to returning. A first dose is useful; a completed series is the plan.
Practical takeaways
- Separate source HBsAg status from the survivor’s documented vaccine status.
- Unknown source plus no reliable completed-series record: give hepatitis B vaccine; do not add HBIG by reflex.
- Known HBsAg-positive source plus an unvaccinated or incompletely vaccinated survivor: give vaccine and HBIG, then complete the series.
- A completed series with documented response is different from a completed series with no post-vaccination testing; follow the sexual-assault-specific booster guidance for the latter.
- Start as soon as possible, do not wait for records or serology, and make follow-up actionable.
