COVID-19 is a fast-invading virus that quickly invaded the human body and made no human activity immune to its infections. The purpose of this study is to simulate the effects of COVID-19 on employment behaviour and vaccination’s weight in the recovery process. Based on quarterly panel data from 43 nations from 2018 to 2020, we built an adaptive employment model. The major findings demonstrate that COVID-19 has negative and large net and second effects, with parameters of −7049 and −15,768 employees each quarter for 100,000 infected people, respectively. While immunization has a positive net effect of 10,900 employees every quarter, it has a negative second effect of −29,817 employees. This last result may look strange, but it is rational and demonstrates that immunizations modify employees’ behaviour toward prevention measures, leading to actions such as resuming mobility, reopening, cancelling confinement, and so on, even though COVID-19 continues to spread. Demand, the labour force, the short-term multiplier, and immunization appear to have a positive and large impact on employment behaviour, while average labour productivity appears to have a negative impact.