Merge pull request #384 from cmu-delphi/docs/survey-v4-aggregates

Document upcoming V4 aggregates

Author: capnrefsmmat

docs/api/covidcast-signals/fb-survey.md

@@ -325,7 +325,12 @@ also available. These have names beginning `smoothed_w`, such as
 | Signal | Description | Survey Item |
 | --- | --- | --- |
 | `smoothed_accept_covid_vaccine` | Estimated percentage of respondents who would definitely or probably choose to get vaccinated, if a COVID-19 vaccine were offered to them today. **Note:** Until January 6, 2021, all respondents answered this question; beginning on that date, only respondents who said they have not received a COVID vaccine are asked this question. <br/> **First Available:** 2021-01-01 | V3 |
-| `smoothed_covid_vaccinated` | Estimated percentage of respondents who have already received a vaccine for COVID-19. **Note:** The Centers for Disease Control compiles data on vaccine administration across the United States. This signal may differ from CDC data because of survey biases and should not be treated as authoritative. However, the survey signal is not subject to the lags and reporting problems in official vaccination data. <br/> **First Available:** 2021-06-01 | V1 |
+| `smoothed_covid_vaccinated` | Estimated percentage of respondents who have already received a vaccine for COVID-19. **Note:** The Centers for Disease Control compiles data on vaccine administration across the United States. This signal may differ from CDC data because of survey biases and should not be treated as authoritative. However, the survey signal is not subject to the lags and reporting problems in official vaccination data. <br/> **First Available:** 2021-01-06 | V1 |
+| `smoothed_vaccine_likely_friends` | Estimated percentage of respondents who would be more likely to get a COVID-19 vaccine if it were recommended to them by friends and family, among respondents who have not yet been vaccinated. <br/> **First Available:** 2021-01-20 | V4 |
+| `smoothed_vaccine_likely_local_health` | Estimated percentage of respondents who would be more likely to get a COVID-19 vaccine if it were recommended to them by local health workers, among respondents who have not yet been vaccinated. <br/> **First Available:** 2021-01-20 | V4 |
+| `smoothed_vaccine_likely_who` | Estimated percentage of respondents who would be more likely to get a COVID-19 vaccine if it were recommended to them by the World Health Organization, among respondents who have not yet been vaccinated. <br/> **First Available:** 2021-01-20 | V4 |
+| `smoothed_vaccine_likely_govt_health` | Estimated percentage of respondents who would be more likely to get a COVID-19 vaccine if it were recommended to them by government health officials, among respondents who have not yet been vaccinated. <br/> **First Available:** 2021-01-20 | V4 |
+| `smoothed_vaccine_likely_politicians` | Estimated percentage of respondents who would be more likely to get a COVID-19 vaccine if it were recommended to them by politicians, among respondents who have not yet been vaccinated. <br/> **First Available:** 2021-01-20 | V4 |
 
 These indicators are based on questions added in Wave 6 of the survey,
 introduced on December 19, 2020; however, Delphi only enabled item V1 beginning