Coronavirus (COVID-19): modelling the epidemic (issue no. 49)

Key Points

• The reproduction rate R in Scotland is currently estimated as being between 0.8 and 1.0. The range limits are higher than last week.
• The number of new daily infections for Scotland is estimated as being between 1 and 15, per 100,000 people. The range limits are lower than last week.
• The growth rate for Scotland is currently estimated as being between -4% and -1%. This is the same as last week.
• Average contacts are still higher than seen during the lockdown period (when it averaged around 3 daily contacts) with a current level of 3.3 daily contacts.
• Contacts within the work and school setting have shown a decrease in the last two weeks by 32% and 88% respectively.
• Mean contacts within the 'other' setting (contacts outside of the school, home or work settings) have increased by approximately 11%.
• Individuals aged 60 and over have increased their contacts in the last two weeks, while average contacts for those aged under 60 have remained level or have shown a decrease.
• The 18-39 age group has shown a decrease in interactions with individuals under 18 whereas those aged 40-49 have increased their interactions with this age group.
• The biggest change in the proportion of participants visiting different locations is seen in those visiting a hairdressers/beauticians^[1], increasing from less than 1% to 20% in the last two weeks, followed by visits to non-essential shops^[2], increasing from 14% to 22%.
• Hospital bed and ICU occupancy are projected to fall over the next few weeks, but these both may plateau or increase as a result of all schools reopening and other relaxations of non-pharmaceutical interventions.
• A major study reported in the Lancet^[3] investigated the association between mass roll-out of the first doses of vaccines and hospital admissions in Scotland for COVID-19. Four weeks after receiving a first dose, the Pfizer-BioNTech vaccine was shown to reduce the risk of COVID-19 hospitalisation by 91% (95% CI 85 – 94), and the Oxford-AstraZeneca vaccine by 88% (95% CI 75 – 94). These results show an association with substantial reductions in the risk of COVID-19 hospitalisations across Scotland.
• There were 4 local authority areas which exceeded what would be expected at this stage in the epidemic between 20-26 April. Dumfries and Galloway, Moray, Inverclyde and Glasgow City were areas of higher risk of transmission.
• Modelled rates per 100K indicate that for the week commencing 9 May 2021 no local authorities have at least a 75% probability of exceeding 50 cases. This is the same as last week.