PhD defence Charlotte Martin

Supervisors

• Prof. dr. Emmanuel Bottieau (ITM)

• Dr. Nicolas Dauby (ULB)

• Prof. dr. Stéphane De Wit (ULB) 

Abstract

Since the advent of modern and universal ART in our countries, PLWH have a life expectancy and lifestyle comparable to the general population. Many of them are travelling, either for tourism or to visit friends and relatives (VFR), including to yellow fever (YF) endemic destinations. They are therefore likely to be vaccinated against yellow fever. Since 2016, WHO guarantees administrative validity for life after YF vaccination, except for PLWH due to a lack of data on the subject. PLWH probably require a specific YF vaccination schedule but there is not enough rational basis for its elaboration. This work has several objectives. We first wanted to characterize the travel of our cohort of PLWH: whether PLWH travelled to YF endemic areas, and whether they consulted appropriately before travel. We have indeed highlighted that the proportion of travellers is significant, and that VFR travellers represent a significant proportion, particularly in YF endemic areas. We then conducted a systematic literature review on the yellow fever vaccination in PLWH, to identify current knowledge and knowledge gaps. We were able to show that the seroconversion rate after YF vaccination is high in PLWH especially when the HIV viral load is controlled. However, it is followed by a rapid NAbs decay, sometimes in the first 5 years after YF vaccination, and more than 10 years after YF vaccine, the NAbs positivity rate is only between 45% and 78%. We confirmed these data with a study on a cohort of PLWH followed in Belgium and vaccinated against yellow fever. This work also allowed to highlight two important observations: the ability of PLWH to respond to revaccination and a possible benefit of YF revaccination in PLWH on the duration of protection by vaccination. Finally, we studied the same elements and determinants in a cohort of subjects with perinatally-acquired HIV (pHIV) vaccinated against yellow fever, which had never been studied before. This showed that 85% of vaccinees experienced seroconversion after YF vaccination but suggested also that YF revaccination could be necessary to ensure the long-term persistence of NAbs in subjects with pHIV. In conclusion, we have been able to put together several elements to develop a proposal for a specific vaccination program against YF for PLWH even if several questions remain to be studied in the future.