Technical note: SARS-CoV-2 variants and vaccination in Belgium (v2022-02-08)
The SIMID consortium prepared a new technical note (v2022-02-08) containing the estimates of a stochastic dynamic transmission model using observational data up to February 4th, 2022.
We explored the impact of the Omicron Variant of Concern (VOC) for Belgium with a country-level stochastic transmission model that incorporates infection- and vaccine-induced immunity levels in the population. By combining data from the baseline genomics surveillance of SARS-COV-2 with estimated transmission dynamics for Belgium, the model projects decreasing numbers of infections and hospitalisations by the Omicron VOC in the coming weeks.
Exploring different scenarios of increased transmission rates with relatively high and low protection of current vaccines against infection and severe disease by Omicron, we project a limited resurgence of hospital admissions. The rise in transmission potential could be due to adapted social contact behaviour, increased infectiousness of an Omicron sub-strain (e.g., BA.2), or both.
Given our focus on severe disease and hospital admissions, we assume no waning of vaccine-induced immunity after booster vaccination doses over the time span considered in this note. The incidence of breakthrough-infections in the scenarios could still cause a burden on primary care. This should be revisited when new information becomes available.
We are making the implicit assumption that the Omicron VOC will remain the dominant strain throughout the entire simulation period. Nonetheless, other (new emerging) VOCs may have different transmission probabilities and probabilities to cause disease, hospitalization, death, and different vaccine effectiveness characteristics against each of these manifestations.
The national model does not account for local differences in immunity and clustered social contact networks. General trends are captured well, though local outbreaks are underestimated and herd immunity effects are overestimated in sub-populations with immunity levels below the national level, and the reverse may be true in sub-populations with higher than average immunity.
The full document from February 2022 (v2022-02-08) is available here.