US model limits monkeypox infections by one-third from having fewer one-time partners: short-term strategy until next vaccine supply

Simon Collins, HIV i-Base

A modelling paper, published in the MMWR, supports the importance of reducing the number of one-time sexual partners as a strategy to manage the current monkeypox (MPX) crisis. [1]

In addition to significantly reducing the risk of new infections, perhaps by up to one-third, this would buy time until new vaccine supplies become available – expected in the next month.

The model projected that among a population of 10,000 gay men, ten highly active individuals could lead to 1,500 to 2,500 infections (15-25%), depending on different transmission scenarios.

In this setting, approximately 50% of all monkeypox (MPX) cases are linked to one-time sexual partnerships, even though they only account for 16% of daily sex acts and 3% of daily sex partnerships.

The model predicted that reducing one-time partnerships by 40% could reduce new cases by approximately 20-30%, and that these gains would be increased if combined with other changes in risk.

Importantly, this level of risk reduction has already been reported in at least one US survey. [2, 3]


Behavioural changes now to reduce the number of MPX cases is a short-term strategy to block the current outbreak and enable the vaccine programme to be more effective. [4]

MPX vaccine supplies are already exhausted in the UK, with the next shipment of 100,000 vials expected by late September. [5]

The move to intradermal vaccination, pending results from a UK pilot study, might also enable up to five doses from each vial that is currently approved to give a single subcutaneous shot. [6]

Although divided dosing is being used in the US, initial practical difficulties have also been reported. These include retraining nurses, needing different syringes, contraindication with hisotry of keloids, and community information. [7]


  1. Spicknall IH et al. Modeling the impact of sexual networks in the transmission of monkeypox virus among gay, bisexual, and other men who have sex with men — United States, 2022. DOI: 10.15585/mmwr.mm7135e2. ePub: 26 August 2022.
  2. Monkeypox changes sexual behaviour in 50% of gay men in US survey. HTB (1 September 2022).
  3. Delaney KP et al. Strategies adopted by gay, bisexual, and other men who have sex with men to prevent monkeypox virus transmission — United States, August 2022. DOI: 10.15585/mmwr.mm7135e1. ePub: 26 August 2022.
  4. Taking a break from monkeypox: four weeks out for August (and also September). HTB (3 August 2022).
  5. Medscape. Monkeypox vaccination to run out next week until new supply delivered. (15 August 2022).
  6. UKHSA. Intradermal monkeypox vaccination for eligible patients. (22 August 2022).
  7. POLITICO. White House strategy for monkeypox vaccines causing ‘chaos out in the field’. (24 August 2022).

Links to other websites are current at date of posting but not maintained.