  For countries starting to receive steady supplies of vaccines against
SARS-CoV-2, the course of Covid-19 for the following months will be determined
by the emergence of new variants and successful roll-out of vaccination
campaigns. To anticipate this scenario, we used a multilayer network model
developed to forecast the transmission dynamics of Covid-19 in Costa Rica, and
to estimate the impact of the introduction of the Delta variant in the country,
under two plausible vaccination scenarios, one sustaining Costa Rica's July
2021 vaccination pace of 30,000 doses per day and with high acceptance from the
population and another with declining vaccination pace to 13,000 doses per day
and with lower acceptance. Results suggest that the introduction and gradual
dominance of the Delta variant would increase Covid-19 hospitalizations and ICU
admissions between $35\%$ and $33.25\%$, from August 2021 to December 2021,
depending on vaccine administration and acceptance. In the presence of the
Delta variant, new Covid-19 hospitalizations and ICU admission would experience
an average increase of $24.26\%$ and $27.19\%$ respectively in the same period
if the vaccination pace drops. Our results can help decision-makers better
prepare for the COVID-19 pandemic in the months to come.
