Technical note: SARS-CoV-2 variants and vaccination in Belgium (v2021-04-15)
The SIMID consortium prepared a second technical note (v2021-04-15) containing the model estimates of potential short and long term hospital and ICU admissions and load using observational data up to April 13th, 2021, by a short-term prediction model on the one hand, and a stochastic dynamic transmission model on the other.
Preliminary conclusions
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The age-specific vaccination uptake and the higher transmissibility and severity of variants of concern (VOC), primarily VOC-202012/1 or lineage B.1.1.7, have caused a change in the relation between confirmed COVID-19 cases, daily number of new hospitalizations, hospital load, ICU load and number of COVID-19 related deaths (see e.g. Davies et al. 2021, Patone et al. 2021).
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The short term prediction model depicts a further increase in new hospitalizations and ICU load, driven by the current increase in positivity ratio in some provinces and the observed mobility patterns.
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Dynamic stochastic modelling of the underlying mechanisms informed by empirical social contact data up to April 6th, 2021, shows a decrease in new hospital admissions by the end of April. The projected hospital load corresponds to 2000 occupied hospital beds, on average, and an ICU load between 400-800 beds by May 1st, 2021. However, these projections show large credible intervals and should be interpreted with care. Especially the relationship between hospital admissions and ICU load is still under scrutiny.
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Model scenarios assuming a shift in behavior (and transmission) on 19-24 April, 2021, in line with the situation of 1-24 March, 2021, show a plateau in hospital admissions in May-June 2021.
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Model scenarios assuming also a change in behavior in May 2021, show a resurgence of the hospital admissions and associated occupancy in ICU and non-ICU. This is more pronounced when this behavioural change occurs from the 1st of May, instead of from the 15th of May onwards.
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Vaccine uptake is shown to be influential for the magnitude of the above described resurgence and associated pressure on tertiary health care, but vaccination at expected uptake levels is likely unable to prevent it.
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Counterfactual scenarios in which we exclude all vaccine-related protection show hospital admissions and loads that are 2-3 times higher by May 2021 and rise beyond the second wave peak observed in November 2020.