Key signatories of John Snow Memorandum (JSM) or Great Barrington Declaration (GBD) with over 50 000 Twitter followers as of April 2021: citation impact, H-index and K-index
| Scientist | Twitter followers (April 2021)* | Twitter followers (November 2021)* | Citations | H-index | K-index |
| Deepti Gurdasani (JSM) | 50 400 | 103 900 | 5799 | 19 | 454 |
| Angela Rasmussen (JSM) | 210 800 | 283 900 | 1378 | 18 | 1931 |
| Dominic Pimenta (JSM) | 53 900 | 58 300 | 37 | 2 | 997 |
| Trisha Greenhalgh (JSM) | 121 700 | 150 000 | 28 003 | 81 | 689 |
| Nisreen Alwan (JSM) | 50 700 | 69 100 | 1059 | 19 | 456 |
| Emma Hodcroft (JSM) | 56 900 | 65 700 | 577 | 13 | 578 |
| Florian Krammer (JSM) | 192 600 | 232 300 | 11 288 | 61 | 1194 |
| Marc Lipsitch (JSM) | 226 900 | 235 800 | 23 565 | 82 | 1279 |
| Devi Sridhar (JSM) | 281 100 | 310 100 | 2720 | 23 | 2380 |
| Rochelle Walensky (JSM) | 90 000 | 345 800 | 10 561 | 54 | 580 |
| Karol Sikora (GBD) | 330 300 | 331 800 | 4401 | 30 | 2569 |
| Michael Levitt (GBD) | 86 900 | 105 300 | 40 731 | 106 | 451 |
| Martin Kulldorff (GBD) | 58 800 | 171 300 | 14 081 | 62 | 363 |
Only scientists with >50 000 Twitter followers as of April 2021 are shown in the table. As explained in the asterisk footnote below, by November 2021, there were three more John Snow Memorandum key signatories (Isabella Eckerle, Zoe Hyde, Viola Priesemann) who had increased their Twitter followers to >50 000 and one more Great Barrington Declaration signatory (Jay Bhattacharya) who had acquired a Twitter account in the meanwhile and had also exceeded 50 000 Twitter followers. H-indices in November 2021 were 26 for Isabella Eckerle, 22 for Zoe Hyde, 21 for Viola Priesemann and 37 for Jay Bhattacharya.
*Twitter followers for other key signatories in April 2021 and (in parenthesis) in November 2021: Rochelle A. Burgess 3281 (4504), Simon Ashworth 8246 (9124), Rupert Beale 15 500 (19 200), Nahid Bhadelia 33 700 (39 400), Debby Bogaert 2574 (3030), Jenn Dowd 6933 (7221), Isabella Eckerle 48 800 (61 200), Lynn R Goldman 909 (922), Adam Hamdy 10 100 (12 000), William Hanage 39 500 (48 700), Zoe Hyde 39 100 (55 300), Paul Kellam 1069 (1107), Michelle Kelly-Irving 10 200 (10 500), Alan McNally 16 300 (19 300), Martin McKee 33 800 (40 300), Ali Nouri 31 600 (34 600), Viola Priesemann 37 700 (54 900), Harry Rutter 8714 (8859), Joshua Silver 13 300 (15 800), Charles Swanton 7724 (8721), Gavin Yamey 10 200 (26 100), Hisham Ziauddeen 2025 (9795) for JSM; and Andrius Kavaliunas 182 (3479), Ariel Munitz 952 (1013), David Katz 46 000 (46 000), Eyal Shahar 2619 (6152), Gabriela Gomes 10 500 (14 400), Gerhard Krönke 69 (117), Jonas Ludvigsson 2693 (7140), Lisa White 586 (642), Matthew Strauss 14 200 (22 700), Rajiv Bhatia 187 (1525), Salmaan Keshavjee 1955 (2213), Simon Thornley 520 (1207), Sylvia Fogel 614 (3405), Udi Qimron 2695 (4374), Yaz Gulnur Muradoglu 26 (39) for GBD. No personal Twitter accounts were found for the remaining GBD signatories in April 2021, but three of them had detectable Twitter accounts in searches done in November 2021 (Ellen Townsend 18 400 followers, Stephen Bremner 15 followers, Jay Bhattacharya 80 800 followers).