Universal suffrage was introduced in Antigua and Barbuda in 1951 (National Encyclopedia, "Antigua and Barbuda- Politics, government, and taxation"). Antigua and Barbuda’s 1981 Constitution contains the first assertion of the right to vote in the country’s independent history. Section 40 specifically outlines this right.

References:

The 1981 Constitution of Antigua and Barbuda: https://www.legislation.gov.uk/uksi/1981/1106/pdfs/uksi_19811106_en.pdf

National Encyclopedia: https://www.nationsencyclopedia.com/economies/Americas/Antigua-and-Barbuda-POLITICS-GOVERNMENT-AND-TAXATION.html#google_vignette