{"id":52764,"date":"2025-11-23T21:34:21","date_gmt":"2025-11-23T21:34:21","guid":{"rendered":"https:\/\/i-base.info\/htb\/?p=52764"},"modified":"2025-12-13T08:03:56","modified_gmt":"2025-12-13T08:03:56","slug":"urgency-of-starting-pep-asap-after-sex-predicting-the-impact-on-efficacy-and-previous-prep","status":"publish","type":"post","link":"https:\/\/i-base.info\/htb\/52764","title":{"rendered":"Importance of rapid PEP: predicting impact of delay and duration of 2- and 3-drug PEP"},"content":{"rendered":"

Simon Collins, HIV i-Base<\/strong><\/p>\n

A modelling analysis predicting the impact of time taken to initiate PEP was published in a supplement to JIAS. [1]<\/strong><\/p>\n

The results include using either 2-drug or 3-drug PEP and are for continuing PEP for 2 weeks vs 4 weeks.<\/p>\n

The paper includes a useful practical table (see below) that estimates subsequent PEP efficacy, including 95% confidence intervals. It also shows no impact from continuing PEP out to 7 weeks.<\/p>\n

For example, for 2-drug PEP to be effective it really needs to be started within an hour (assuming PrEP was not recently used).<\/p>\n

By contrast, 3-drug PEP is still highly effective even if the first dose is delayed by 24 hours, and even if PEP is only continued for 2 weeks. Four weeks of 3-drug PEP remains 88% effective if started between 24-48 hours, but drops to 50% efficacy if not started until 72 hours after sex.<\/p>\n

The study also supported the impact of starting PEP with an initial dose of PrEP, as already introduced in the recent UK PrEP guidelines. [2]<\/p>\n

Although only modelling data, these results support further clinical research into easier options for shorter course PEP. The study also shows limited differences between dolutegravir- vs efavirenz-based PEP, even though efavirenz is not a recommended option for PEP.<\/p>\n

It would be interesting to see the 2-drug PEP modelling use an initial double-dose because of the significant pharmacokinetic advantages. [2]<\/p>\n

Table 1. Impact on delays of initiating PEP with 2- and 3-drug combinations<\/h3>\n
\"\"<\/a>

Impact on delays of initiating PEP with 2- and 3-drug combinations (click for large view)<\/p><\/div>\n

Note: Simon Collins is also a co-author of the JIAS paper.<\/em><\/p>\n

References<\/p>\n

    \n
  1. Zhang L et al. Modelling the impact of initiation delay, duration and prior PrEP on the efficacy of post-exposure prophylaxis containing a tenofovir\/emtricitabine backbone. J Int AIDS Soc. Volume 28 Issue Supplement 1: PEP in Africa: prospects, opportunities and challenges. 28: e26454. 26 June 2025. DOI: 10.1002\/jia2.26454
    \n    https:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/jia2.26454<\/a><\/li>\n
  2. BASHH\/BHIVA. Guideline on the Use of HIV Pre-exposure Prophylaxis (2025)
    \n    https:\/\/www.bashh.org\/resources\/5\/hiv_preexposure_prophylaxis_2018<\/a> [sic]
    \n    https:\/\/www.bashh.org\/_userfiles\/pages\/files\/prep_2025.pdf<\/a>\u00a0(PDF)<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    Simon Collins, HIV i-Base A modelling analysis predicting the impact of time taken to initiate PEP was published in a supplement to JIAS. [1] The results include using either 2-drug or 3-drug PEP and are for continuing PEP for 2 …<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[343,10],"tags":[],"class_list":["post-52764","post","type-post","status-publish","format-standard","hentry","category-journal-scan","category-transmission-and-prevention"],"_links":{"self":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/posts\/52764","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/comments?post=52764"}],"version-history":[{"count":5,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/posts\/52764\/revisions"}],"predecessor-version":[{"id":52954,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/posts\/52764\/revisions\/52954"}],"wp:attachment":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/media?parent=52764"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/categories?post=52764"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/tags?post=52764"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}