Table 1.
Characteristics of the study subjects.
| Variable | Value | % |
|---|---|---|
| Year of Birtha | 2005(443523) | 7.8 |
| 2006(456209) | 8.0 | |
| 2007(501126) | 8.8 | |
| 2008(519361) | 9.1 | |
| 2009(532126) | 9.3 | |
| 2010(543753) | 9.5 | |
| 2011(619650) | 10.8 | |
| 2012(684232) | 12.0 | |
| 2013(705528) | 12.3 | |
| 2014(717227) | 12.5 | |
| Gender | Male | 51.1 |
| Female | 48.9 | |
| Socio-economic stratab | Low (5 municipals) | 29.9 |
| Middle (3 municipals) | 34.9 | |
| High (3 municipals) | 35.2 | |
| Immigration status of children | Resident | 64.1 |
| Migrant | 35.9 | |
| Race | Han | 93.7 |
| Other minorities | 6.3 | |
| Place of delivery | Home | 4.2 |
| Hospital | 95.8 | |
| Receipt of MMR | No | 3.9 |
| Yes | 96.1 | |
| Receipt of VarV | No | 24.7 |
| Yes | 75.3 |
Note:
a
: the number of children for each birth cohort was listed.
b
: All of the 11 municipals were divided into 3 socio-economic strata (high, middle, and low) by Gross Domestic Product (GDP) per capita level according to the 2016 statistics of Zhejiang province. Hangzhou, Ningbo and Zhoushan were classified as high socio-economic development areas for GDP per capita >15000 USD. Shaoxing, Jiaxing and Huzhou were classified as middle socio-economic development areas for GDP per capita between 10000 and 15000 USD. Wenzhou, Taizhou, Jinhua, Quzhou and lishui were classified as low socio-economic development areas for GDP per capita < 10000 USD