Table 2.

Definition of key terms and group labels as per used in this study.

Key term	Definition
Vaccine confidence	Level of trust in the safety of childhood vaccinations measured by one's level of agreement to the statement that it is safe to vaccinate children following the NZ immunisation schedule. Having ‘strong vaccine confidence’ indicates that one has a high level of trust in and very minimal or no concerns about childhood vaccine safety.
Vaccine believers	Those that consistently expressed high levels of agreement to the statement that it is safe to vaccinate children following the NZ immunisation schedule during 2013 to 2017. Reasons for their ‘strong vaccine confidence’ may be diverse. This may include general trust in science or vaccinations specifically, better access to healthcare and/or positive perceptions of healthcare professionals or the government.
Vaccine skeptics	Those that showed decreasing levels of agreement to the statement that it is safe to vaccinate children following the NZ immunisation schedule from 2013 to 2017. Opposed to ‘vaccine believers’, reasons for decreasing ‘vaccine confidence’ may include increased exposure to anti-vaccine information, distrust in health professionals and/or limited access to healthcare or vaccine information. These individuals may be expressing diminishing belief in the safety of specific vaccines or vaccinations in general.
Former skeptics	Those that formerly showed the lowest level of agreement to the statement that it is safe to vaccinate children following the NZ immunisation schedule in 2013 but exhibited a steep increase in ‘vaccine confidence’ thereafter (until 2017). This increase could be due to multiple factors, including satisfactory follow-up vaccine conversations with doctors, corrected misconceptions about specific vaccines or vaccinations in general and/or improved access to healthcare.