Researchers at the University of Rostock in Germany have developed a model for the transmission of coronavirus disease 2019 (COVID-19) that takes into account subdivisions of age and gender in order to gain better insights into the effects that increased contact rates have on the risk of infection and mortality could have.
The study’s authors, Achim Doerre and Gabriele Doblhammer, say the number of COVID-19 infections will have doubled by the end of October under current mitigation measures introduced from mid-August, with active cases higher among young people of working age . and the elderly.
For people of working age, the risk of infection would be higher in women than in men, while in older people the risk in men is higher than in women.
In all age groups, the death rate for men would be twice that for women.
The team says the results underscore the importance of non-pharmaceutical mitigation measures (NPMM) in countering the higher risk of mortality that increased contact rates pose for the elderly.
They also say that age- and gender-based models improve infection and mortality predictions, and that such models could be used to guide health policies and prioritize who should be tested and vaccinated first.
A pre-print version of the paper is available on the medRxiv * server while the article is being peer reviewed.
Since the COVID-19 outbreak began late last year in Wuhan, China, researchers have recognized age as a factor influencing the risk of transmission.
Gender ratio (male / female) of the COVID-19 incidence up to May 15, 2020 for German countries by age, data source: Robert Koch Institute Dashboard, author calculations
A new model based on three scenarios
Models that were developed for the spread of diseases have therefore consistently taken age into account as an important transmission variable. Another important determinant, however, is gender, which seems to have been overlooked in previous modeling approaches, say the authors.
Now, Doerre and Doblhammer have developed a COVID-19 transmission model that includes age- and gender-specific contact rates to study the effects of changes in mitigation measures on infection and death rates in men and women in different age groups.
The model was used to develop scenarios in which continued distancing measures against relaxation of contact restrictions in different subdivisions by age group and gender were assumed. Three scenarios have been developed with projections starting on August 15, 2020 and ending on October 31, 2020.
The first scenario reflects a continuation of the distancing measures applied in mid-August and assumes that age and gender-specific contacts will be reduced by 80%.
The second scenario implies lifting measures, especially at working age, and should reflect return from work and reopening of facilities such as shops, cafes and restaurants.
The third scenario extends the growth in contacts with children, adolescents and young adults to reflect the reopening of schools and venues that are mostly attended by young people.
Ratio of the average number of contacts between men and women, data source: (van de Kassteele et al. (2017)).
What did the study find out?
The model predicted that the number of COVID-19 cases under the control measures currently in place in mid-August would roughly double by the end of October and increase from 10,572 on August 15, 2020 to 19,814 by October 31.
The authors say that three important lessons could be learned from the scenarios generated by the model.
First, just a small change in contact rates would have a significant impact on infection and mortality rates.
“This means that the impact of contacts must be significantly reduced in order to allow an increase in contacts without returning to an exponential growth in infections, which underscores the great importance of the NPMM in the current phase of the pandemic,” the team writes.
Second, intergenerational contact would mean that relaxation of mitigation measures among young people and of working age would lead to the highest infection rate among these age groups and increased infection rates among the elderly.
Older people would be at the highest risk of death, older men always at a higher risk than women.
“Increased contact must be accompanied by special measures to protect the elderly from death, without negative effects on physical and mental health due to quarantine and isolation measures,” the authors say.
Third, a small increase in contact rates would not change the infection and death rate of the sex relationship. Women of working age are at higher risk of infection than men, while older men are the opposite, and men are twice as likely to die in all age groups as women.
How can the model help?
The researchers say that while the predictions of this model differ only slightly from those of non-gender models, age- and gender-specific models provide better insights into the population’s risk of infection and mortality.
Using such models would help public health interventions target those who should be tested and vaccinated first.
The effects of biological sex and gender on COVID-19 infection rates and outcomes must be considered in health policy and treatment decisions, the team concludes.
* Important NOTE
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or be treated as established information.