1. Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S, et al. Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine. N Engl J Med. 2020; 383(27):2603–2615. PMID:
33301246.

2. Folegatti PM, Ewer KJ, Aley PK, Angus B, Becker S, Belij-Rammerstorfer S, et al. Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2: a preliminary report of a phase 1/2, single-blind, randomised controlled trial. Lancet. 2020; 396(10249):467–478. PMID:
32702298.
3. Ramasamy MN, Minassian AM, Ewer KJ, Flaxman AL, Folegatti PM, Owens DR, et al. Safety and immunogenicity of ChAdOx1 nCoV-19 vaccine administered in a prime-boost regimen in young and old adults (COV002): a single-blind, randomised, controlled, phase 2/3 trial. Lancet. 2021; 396(10267):1979–1993. PMID:
33220855.
4. Walsh EE, Frenck RW Jr, Falsey AR, Kitchin N, Absalon J, Gurtman A, et al. Safety and immunogenicity of two RNA-based COVID-19 vaccine candidates. N Engl J Med. 2020; 383(25):2439–2450. PMID:
33053279.

5. Dagan N, Barda N, Kepten E, Miron O, Perchik S, Katz MA, et al. BNT162b2 mRNA COVID-19 vaccine in a nationwide mass vaccination setting. N Engl J Med. 2021; 384(15):1412–1423. PMID:
33626250.

6. Kim JY, Bae S, Park S, Kwon JS, Lim SY, Park JY, et al. Comparison of antibody and T cell responses induced by single doses of ChAdOx1 nCoV-19 and BNT162b2 vaccines. Immune Netw. 2021; 21(4):e29. PMID:
34522442.

7. Shrotri M, Fragasz E, Geismar C, Nguyen V, Beale S, Braithwaite I, et al. Spike-antibody responses following first and second doses of ChAdOx1 and BNT162b2 vaccines by age, gender, and clinical factors - a prospective community cohort study (Virus Watch). medRxiv. Forthcoming. 2021; DOI:
10.1101/2021.05.12.21257102.

8. Schwarz T, Tober-Lau P, Hillus D, Helbig ET, Lippert LJ, Thibeault C, et al. Delayed antibody and T-cell response to BNT162b2 vaccination in the elderly, Germany. Emerg Infect Dis. 2021; 27(8):2174–2178. PMID:
34102097.

9. Müller L, Andrée M, Moskorz W, Drexler I, Walotka L, Grothmann R, et al. Age-dependent immune response to the Biontech/Pfizer BNT162b2 COVID-19 vaccination. Clin Infect Dis. 2021; ciab381. PMID:
33906236.

10. Jung J. Preparing for the coronavirus disease (COVID-19) vaccination: evidence, plans, and implications. J Korean Med Sci. 2021; 36(7):e59. PMID:
33619920.

12. Campi-Azevedo AC, Peruhype-Magalhāes V, Coelho-Dos-Reis JG, Antonelli LR, Costa-Pereira C, Speziali E, et al. 17DD yellow fever revaccination and heightened long-term immunity in populations of disease-endemic areas, Brazil. Emerg Infect Dis. 2019; 25(8):1511–1521. PMID:
31298654.

13. Cohen BJ, Doblas D, Andrews N. Comparison of plaque reduction neutralisation test (PRNT) and measles virus-specific IgG ELISA for assessing immunogenicity of measles vaccination. Vaccine. 2008; 26(50):6392–6397. PMID:
18834911.

14. Eyal O, Olshevsky U, Lustig S, Paran N, Halevy M, Schneider P, et al. Development of a tissue-culture-based enzyme-immunoassay method for the quantitation of anti-vaccinia-neutralizing antibodies in human sera. J Virol Methods. 2005; 130(1-2):15–21. PMID:
16024096.

15. Tan CW, Chia WN, Qin X, Liu P, Chen MI, Tiu C, et al. A SARS-CoV-2 surrogate virus neutralization test based on antibody-mediated blockage of ACE2-spike protein-protein interaction. Nat Biotechnol. 2020; 38(9):1073–1078. PMID:
32704169.

16. Walls AC, Park YJ, Tortorici MA, Wall A, McGuire AT, Veesler D. Structure, function, and antigenicity of the SARS-CoV-2 spike glycoprotein. Cell. 2020; 181(2):281–292.e6. PMID:
32155444.

17. Dai L, Gao GF. Viral targets for vaccines against COVID-19. Nat Rev Immunol. 2021; 21(2):73–82. PMID:
33340022.

18. Salvatori G, Luberto L, Maffei M, Aurisicchio L, Roscilli G, Palombo F, et al. SARS-CoV-2 SPIKE PROTEIN: an optimal immunological target for vaccines. J Transl Med. 2020; 18(1):222. PMID:
32493510.

19. Buchholz UJ, Bukreyev A, Yang L, Lamirande EW, Murphy BR, Subbarao K, et al. Contributions of the structural proteins of severe acute respiratory syndrome coronavirus to protective immunity. Proc Natl Acad Sci U S A. 2004; 101(26):9804–9809. PMID:
15210961.

20. Traggiai E, Becker S, Subbarao K, Kolesnikova L, Uematsu Y, Gismondo MR, et al. An efficient method to make human monoclonal antibodies from memory B cells: potent neutralization of SARS coronavirus. Nat Med. 2004; 10(8):871–875. PMID:
15247913.

21. Huang WC, Zhou S, He X, Chiem K, Mabrouk MT, Nissly RH, et al. SARS-CoV-2 RBD neutralizing antibody induction is enhanced by particulate vaccination. Adv Mater. 2020; 32(50):e2005637. PMID:
33111375.

22. Khoury DS, Cromer D, Reynaldi A, Schlub TE, Wheatley AK, Juno JA, et al. Neutralizing antibody levels are highly predictive of immune protection from symptomatic SARS-CoV-2 infection. Nat Med. 2021; 27(7):1205–1211. PMID:
34002089.

23. Kim N, Minn D, Park S, Roh EY, Yoon JH, Park H, et al. Positivity of SARS-CoV-2 antibodies among Korean healthy healthcare workers 1 and 2 weeks after second dose of Pfizer-BioNTech vaccination. J Korean Med Sci. 2021; 36(21):e158. PMID:
34060264.

24. Earle KA, Ambrosino DM, Fiore-Gartland A, Goldblatt D, Gilbert PB, Siber GR, et al. Evidence for antibody as a protective correlate for COVID-19 vaccines. Vaccine. 2021; 39(32):4423–4428. PMID:
34210573.

25. Grzelak L, Temmam S, Planchais C, Demeret C, Tondeur L, Huon C, et al. A comparison of four serological assays for detecting anti-SARS-CoV-2 antibodies in human serum samples from different populations. Sci Transl Med. 2020; 12(559):eabc3103. PMID:
32817357.

26. Muecksch F, Wise H, Batchelor B, Squires M, Semple E, Richardson C, et al. Longitudinal serological analysis and neutralizing antibody levels in coronavirus disease 2019 convalescent patients. J Infect Dis. 2021; 223(3):389–398. PMID:
33140086.

27. Fischinger S, Boudreau CM, Butler AL, Streeck H, Alter G. Sex differences in vaccine-induced humoral immunity. Semin Immunopathol. 2019; 41(2):239–249. PMID:
30547182.

28. Klein SL, Flanagan KL. Sex differences in immune responses. Nat Rev Immunol. 2016; 16(10):626–638. PMID:
27546235.

29. Zimmermann P, Curtis N. Factors that influence the immune response to vaccination. Clin Microbiol Rev. 2019; 32(2):e00084-18. PMID:
30867162.

30. Bunders MJ, Altfeld M. Implications of sex differences in immunity for SARS-CoV-2 pathogenesis and design of therapeutic interventions. Immunity. 2020; 53(3):487–495. PMID:
32853545.

31. Giefing-Kröll C, Berger P, Lepperdinger G, Grubeck-Loebenstein B. How sex and age affect immune responses, susceptibility to infections, and response to vaccination. Aging Cell. 2015; 14(3):309–321. PMID:
25720438.

32. Takahashi T, Ellingson MK, Wong P, Israelow B, Lucas C, Klein J, et al. Sex differences in immune responses that underlie COVID-19 disease outcomes. Nature. 2020; 588(7837):315–320. PMID:
32846427.
33. Flanagan KL, Fink AL, Plebanski M, Klein SL. Sex and gender differences in the outcomes of vaccination over the life course. Annu Rev Cell Dev Biol. 2017; 33(1):577–599. PMID:
28992436.

34. McCartney PR. Sex-based vaccine response in the context of COVID-19. J Obstet Gynecol Neonatal Nurs. 2020; 49(5):405–408.

35. Mueller AL, McNamara MS, Sinclair DA. Why does COVID-19 disproportionately affect older people? Aging (Albany NY). 2020; 12(10):9959–9981. PMID:
32470948.

36. Mahase E. COVID-19: single dose of Pfizer or AstraZeneca vaccine produces strong antibody response in over 80s. BMJ. 2021; 373(979):n979. PMID:
33858846.
