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Acceptance and timeliness of post-exposure vaccination against mpox in high-risk contacts, Amsterdam, the
C E van Ewijk1, C Smit2, R Bavalia2
1Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands; European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden.
Background:
May 2022, several countries reported mpox outbreaks among men-who-have-sex-with-men. In the Netherlands, high-risk contacts were offered the third-generation smallpox vaccine as post-exposure-prophylaxis (PEP) within 4 but maximum 14 days after exposure. We investigated their PEP acceptance, timeliness of uptake and development of mpox for the region of the Public Health Service (PHS) Amsterdam.
Methods:
High-risk contacts identified during 20 May-22 July 2022 were included. Contacts were followed-up 21 days after exposure and classified as: no patient (no mpox symptoms or orthopoxvirus PCR-negative) or mpox patient (clinically suspected mpox or orthopoxvirus PCR-positive). We calculated time intervals between date of last exposure and first PHS consultation, PEP administration, and symptom onset.
Results:
Two-hundred-ninety contacts were at high-risk of mpox predominantly due to sexual and/or direct skin-skin contact (212/290, 73 %). First PHS consultation was a median of 5 (IQR 3, 7) days after exposure, at which point 26/290 (9 %) contacts were ineligible for PEP. 84 % (223/264) of contacts eligible for PEP, received PEP within a median of 6 (IQR 3, 8) days after exposure. Of 282 contacts (missing outcome n = 8) 38 (14 %) developed mpox a median of 7 (IQR 5, 12) days after exposure, of whom 50 % (19/38) developed mpox before their first PHS consultation. Among contacts eligible for PEP, 2/38 (5 %) unvaccinated and 16/218 (7 %) vaccinated contact developed mpox.
Conclusions:
PEP acceptance among contacts of mpox patients was high. However, PEP timeliness was inadequate. Half of contacts received PEP 6 or more days after exposure, and half of contacts who developed mpox had an onset prior to their first PHS consultation. Estimating PEP vaccine effectiveness is problematic due to the timeliness of PEP and the time it takes to generate vaccine-induced immunity. It is important to assess how PEP timeliness may improve and to promote pre-exposure vaccination to control mpox outbreaks.
Insights
Mpox post-exposure prophylaxis (PEP) acceptance was high, but uptake was delayed. Many contacts developed mpox before receiving the vaccine, highlighting the need for timely intervention and pre-exposure vaccination strategies.
Area of Science:
- Epidemiology
- Infectious Diseases
- Vaccinology
Background:
- Mpox outbreaks occurred in 2022, particularly among men who have sex with men.
- Post-exposure prophylaxis (PEP) with a third-generation smallpox vaccine was offered to high-risk contacts in the Netherlands.
- The study focused on PEP acceptance, timeliness, and mpox development in Amsterdam.
Purpose of the Study:
- To investigate the acceptance and timeliness of mpox post-exposure prophylaxis (PEP) among high-risk contacts.
- To determine the rate of mpox development after exposure and assess the impact of PEP.
- To inform strategies for controlling mpox outbreaks through vaccination.
Main Methods:
- Included high-risk contacts identified between May and July 2022.
- Followed up contacts for 21 days to classify them as mpox patients or not.
- Calculated time intervals between exposure, consultation, PEP administration, and symptom onset.
Main Results:
- 290 high-risk contacts were identified, primarily through sexual or skin-to-skin contact.
- 84% of eligible contacts received PEP, but a median of 6 days after exposure.
- 14% of contacts developed mpox, with 50% experiencing symptom onset before their initial public health service consultation.
Conclusions:
- High acceptance of mpox PEP was observed, but timeliness was insufficient.
- Delayed PEP administration and the time to immunity may impact vaccine effectiveness.
- Improved PEP timeliness and promotion of pre-exposure vaccination are crucial for mpox outbreak control.
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