Dynamics of an SIRWS model with waning of immunity and varying immune boosting period.

SIRS models capture transmission dynamics of infectious diseases for which immunity is not lifelong. Extending these models by a compartment for individuals with waning immunity, the boosting of the immune system upon repeated exposure may be incorporated. Previous analyses assumed identical waning rates from to and from to .

Sex differences in the experience of COVID-19 post-traumatic stress symptoms by adults in South Africa.

Background: The COVID-19 pandemic has created multiple mental health challenges. Many residents in South Africa face pre-existing elevated levels of stress and the pandemic may have had varying impacts on sub-populations. The aims of this study were to determine: 1) the factors associated with post-traumatic stress symptoms (PTSS) and 2) sex differences in the factors associated with PTSS in adults residing in South Africa during the COVID-19 pandemic.