Vaccination Coverage for Routine Vaccines and Herd Immunity Levels against Measles and Pertussis in the World in 2019

Abstract

In 2012, the World Health Organization (WHO) established the Global Vaccine Action Plan with the objective to promote essential vaccinations in all countries and achieve at least 90% vaccination coverage for all routine vaccines by 2020. The study assessed the mean percentages of vaccination coverage in 2019 for 13 routine vaccines, vaccination coverage variation from 2015 to 2019, and herd immunity levels against measles and pertussis in 2019 in countries and regions of WHO. In 2019, the mean percentages of vaccination coverage were lower than 90% for 10 (78.9%) routine vaccines. The mean percentages of vaccination coverage also decreased from 2015 to 2019 for six (46.2%) routine vaccines. The prevalence of individuals with vaccine-induced measles immunity in the target measles vaccination population was 88.1%, and the prevalence of individuals with vaccine-induced pertussis immunity in the target pertussis vaccination population was 81.1%. Herd immunity against measles viruses with Ro = 18 was established in 63 (32.5%) countries but not established in any region. Herd immunity against pertussis agents was not established in any country and in any region of WHO. National immunization programs must be improved to achieve ≥90% vaccination coverage in all countries and regions. Likewise, it is necessary to achieve ≥95% vaccination coverage with two doses of measles vaccines and three doses of pertussis vaccines in all countries and regions.

Percentages of Vaccination Coverage Required to Establish Herd Immunity against SARS-CoV-2

“…First, percentages of vaccination coverage that would be required to establish herd immunity against SARS-CoV-2 were determined taking into account SARS-CoV-2 transmissibility and COVID-19 vaccination effectiveness. This method is based on the following assumptions: (1) homogeneous mixing of individuals within the population and (2) homogeneous distribution of protected individuals within the population [ 17 , 18 , 19 , 20 , 21 ]. If the distribution of protected individuals is not homogeneous, required percentages of vaccination coverage would be higher or lower in places with lower or higher levels of protected individuals, respectively.…”

“…Herd immunity against SARS-CoV-2 viruses is defined as the indirect protection of susceptible individuals generated by a prevalence of protected individuals (I). Herd immunity is established in a population when the prevalence of immune or protected individuals is higher than the critical prevalence “herd immunity threshold” (I > I c ) [ 17 , 18 , 19 , 20 , 21 ]. When this occurs, the transmission of SARS-CoV-2 viruses is blocked because the number of susceptible individuals infected per case is lower than 1.…”

“…COVID-19 vaccination programs can establish herd immunity when the prevalence of vaccine-induced protected individuals is equal to or higher than the herd immunity threshold (I v ≥ I c ) [ 20 , 21 ]. In this situation, the average number of infected individuals generated per each infected case is lower than 1, and transmission of SARS-CoV-2 is blocked in the population.…”

“…This method is based on the following assumptions: (1) homogeneous mixing of individuals within the population, (2) homogeneous distribution of infected and vaccine-induced protected individuals within the population, and (3) fully susceptible population [ 17 , 18 , 19 , 20 , 21 ].…”

Seroprevalence Study of Pertussis in Adults at Childbearing Age and Young Infants Reveals the Necessity of Booster Immunizations in Adults in China

“…Vaccination is the most effective way to prevent pertussis. Although the percentages of DTaP vaccination coverage in children aged 3, 4, and 5 months were very high in China in 2019 (99%), pertussis protection in terms of the prevalence of children in the target vaccination population with vaccine-induced pertussis protection (83.8%) was not sufficient to establish herd immunity and block the transmission of B. pertussis with values of Ro ≥ 10 in the community [23]. Since pertussis is common in adolescents, a booster immunization in the age group is recommended in many industrial countries.…”