Use of Bass product diffusion model in forecasting spread of COVID-19 epidemic in India was attempted. Forecasting Models need calibration on the basis of new observation data that flows in and marginal calibration concerns the equality of forecast and actual situation. The Adapted model is being subjected to marginal calibration. In this calibration, model parameters, p, q and o; are
... [Show full abstract] re-estimated on a weekly basis using the observed values of S(t), Y(t) and O(t). The new estimates, so obtained, are then used in the model for forecasting from that point onwards. This article reports the second weekly recalibration since the launch of the forecasting model. The changes in the model parameters have been discussed in terms of their causes and likely implications. Forecasts for the Five weeks during the Month of May based on the original parameters, first calibration and second calibration are reported.