Table 1.

Age group categorization

Age groups	Explanation, rationale
	Vaccination groups were defined by adding the number of months indicated for the first childhood vaccine (e.g. 15 months of age) to the dates of birth. For example, a person born in February 1990 was assigned to age-group ‘Patients vaccinated between 1991–1995’, since this individual received the first measles (MMR) vaccine in May 1991
Patients born before 1969	Unvaccinated patients, wild-type infections. 1969: introduction of measles vaccine in Hungary (live, attenuated Leningrad-16 strain produced in the Soviet Union)
Patients vaccinated between 1969 and 1977	From 1969 to 1974, a single dose of measles vaccine was administered in mass campaigns to persons 9–27 months of age. The recommended age for vaccination was 10 months until 1978, when it was changed to 14 months. After the 1980–1981 epidemics, persons born between 1973 and 1977, who would have received vaccine when the recommended age was 10 months, were revaccinated. After 1989, children were re-vaccinated at the age of 11 years with monovalent measles vaccine in a scheduled manner. Consequently, the first individuals who received a reminder vaccine at the age of 11 were born in 1978. Thus, the cluster of 1969–1977 was the last that did not receive a reminder vaccine at the age of 11 as a part of the official vaccine schedule
Patients vaccinated between 1978 and 1987	These are the first individuals who benefited from the reminder monovalent measles vaccine at the age of 11. In 1999 the administration of trivalent vaccine was started in Hungary, consequently who received the first trivalent vaccine in 1999 were born in 1988
Patients vaccinated between 1988 and 1990	In 1989 the rubella vaccine was introduced, and the monovalent measles reminder vaccine at age 11 was started 1990: Introduction of measles–rubella bivalent vaccines
Patients vaccinated between 1991 and 1995	The administration of the first vaccine at age 14 months lasted from 1978 to 1991 1991: Measles–mumps–rubella trivalent vaccine 1992: MMR vaccine at age 15 months 1996: Introduction of MERCK MMR II – Enders’ Edmonston strain (live, attenuated)
Patients born between 1996 and 1998	1996: Introduction of MERCK MMR II – Enders’ Edmonston strain (live, attenuated) 1999: Measles–mumps–rubella re-vaccination (reminder shot) instead of monovalent measles vaccine 1999: Introduction of GSK PLUSERIX – Measles Schwarz Strain
Patients vaccinated between 1999 and 2002	1999: Introduction of GSK PLUSERIX – Measles Schwarz Strain 2003: Introduction of the GSK PRIORIX vaccine
Patients vaccinated in 2003	2003: Introduction of the GSK PRIORIX vaccine – attenuated Schwarz Measles
Patients vaccinated in 2004–2005	2004–2005: Administration of the MERCK MMR II
Patients vaccinated between 2006 and 2010	2006–2010 (5-year tender): GSK PRIORIX – attenuated Schwarz Measles
Patients vaccinated after 2011	Beginning from 2011 we use a Sanofi-MSD product; MMRvaxPro (Measles virus Enders’ Edmonston strain, live, attenuated) for vaccination and re-vaccination of children; GSK PRIORIX is still on the market, commonly used for vaccination in adulthood
Epidemics: 1973–74: Large epidemics, affecting primarily unvaccinated 6–9 years old children 1980–81: Another significant epidemic, affecting primarily 7–10 years old children 1988–89: Epidemic with high age-specific attack rates of 17–21 years old individuals, who had been vaccinated during the first years of the vaccination programme in Hungary 2017–18: Smaller epidemics with few connected and sporadic cases, derived mainly from virus importation