Table 2: Details of sample replenishment procedures, sample size, and baseline retention rates across C19PRC study survey waves, by country.
| Country | Survey wave | ||||||
|---|---|---|---|---|---|---|---|
| Wave 1 (Baseline) | Wave 2 | Wave 3 | Wave 4 | Wave 5 | Wave 6 | ||
| UK | 23 March-28 March 2020 | 22 April–1 May 2020 | 9 July–9 August 2020 | 25 November–22 December 2020 | 24 March–20 April 2021 | 5 August–28 September 2021 | |
| Sample replenishment | NA | No | Yes | Yes | No | Yes | |
| Total wave sample size | 2,025 | 1,406 | 2,019 | 3,867 | 2,520 | 2,058 | |
| Retention (from baseline) | NA | 69.4% | 57.6% | 62.8% | 57.4% | 54.3% | |
| Republic of Ireland | 31 March–5 April 2020 | 30 April–18 May 2020 | 16 July–8 August 2020 | 2 December–22 December 2020 | 19 March–9 April 2021 | ||
| Sample replenishment | NA | Yes | No | Yes | Yes | ||
| Total wave sample size | 1,041 | 1,032 | 534 | 1,098 | 1,110 | ||
| Retention (from baseline) | NA | 48.6% | 51.8% | 43.0% | 37.5% | ||
| Spain | 7 April–14 April 2020 | 7 May–11 May 2020 | 25 November–7 December 2021 | 15 April–22 April 2021 | |||
| Sample replenishment | NA | No | No | No | |||
| Total wave sample size1 | 1,951 | 1,628 | 1,330 | 1,499 | |||
| Retention (from baseline) | NA | 83.4% | 68.2% | 76.8% | |||
| Italy | 13 July–28 July 2020 | 30 April–18 May 2021 | |||||
| Sample replenishment | NA | No | |||||
| Total wave sample size | 1,038 | 544 | |||||
| Attrition | NA | 52.5% | |||||
1Two participants were aged under 18 years and removed from subsequent analyses.