The basic reproduction number (R0 or R naught) of COVID-19 is between 2 and 3 which means 2 or 3 persons can be infected by 1 COVID-19 positive. Ways to turn the R naught to less than 1 are primarily:
1. The herd immunity. It is a sacrificial mitigation tool to control this disease (COVID-19) while the vaccine or medical cure is still a year away, a place may try not to succumb to COVID-19 by boosting the many's immune systems and then them all become shields of others against the COVID-19 virus. With the herd immunity able to produce antibodies against the virus, the former may also cause benign mutation of the latter for its containment.
2. Quarantine. Applying quarantine may control the spread of the virus by locking down a specific area where COVID-19 is positive. Inside the locked-down area, a lot of protocols, rules, and policies must be implemented such as social distancing, wearing of facemask / PPE's, washing hands with soap and/or applying disinfectant from time to time, isolation, targeted mass testing, contact tracing, and etc. in view of containing the spread of the virus.
3. The combination of the two. Both building herd immunity and quarantine can be applied at a time with some reservations of factors to make measures workable or more effective and efficient.