Vaccination Schedules and COVID-19 Risk

A significant difference in the number of novel coronavirus 2019 (COVID-19) cases and mortality has been noted among different World Health Organization (WHO) regions and countries. We compared the vaccination schedules for 2 countries from WHO Europe Region (Italy and Spain) and 2 countries from WHO Regional Office for the Eastern Mediterranean (Iran and Egypt). Both Iran and Egypt included the Sabin vaccine as part of the obligatory vaccination programs; meanwhile, Italy and Spain used the Salk vaccine. Recently, Iran and Egypt added a single dose of the Salk vaccine to the 6-7 doses of Sabin vaccine because of the new evidence showing that the use of the Salk vaccine in conjunction with Sabin vaccine achieves better mucosal immunity. Italy and Spain used an acellular vaccine against pertussis. Meanwhile, Iran and Egypt used a whole-cell vaccine. Taking into consideration the lower number of deaths in Iran and Egypt compared to Italy and Spain, we could hypothesize that the whole-cell pertussis vaccine could have a cross-immunity against COVID-19. Further research is warranted to identify the main reasons for the lower number of COVID-19 cases and deaths in certain countries in order to control COVID-19.