Mike McCallum (born 7 December 1956) is a Jamaican former professional boxer who competed from 1981 to 1997.
 He is a three-weight world champion, having held the WBA super welterweight title from 1984 to 1988; the WBA middleweight title from 1989 to 1991; and the WBC light heavyweight title from 1994 to 1995.
Sean Mannion (born October 6, 1956 in Rosmuc, Ireland) is a former boxer in the light middleweight division.
 He boxed out of Massachusetts in the United States.
 His most notable bout was against Mike McCallum for the vacant WBA title, which he lost over a fifteen round unanimous decision.
 Newline Films reportedly plans to make a film about his life story.
 In January 2014, "Rocky Ros Muc: Seán Ó Mainnín", a biography about Mannion's life and career was released.
 The book is written in Irish but there are plans afoot to release an English version.
José Alfaro is a Nicaraguan boxer who captured the vacant WBA lightweight title against Thai Prawet Singwancha in a split decision on December 29, 2007 in Bielefeld, Germany.
 He later lost that title on May 19, 2008 to Yusuke Kobori who knocked him out in only 3 rounds.
 His next match was against Mexican legend Erik Morales on March 27, 2010 for the vacant WBC International Welterweight.
 He lost via Unanimous Decision the scores were 117-111, 116-112,116-112.
Bernabe Villacampo (born June 11, 1943) was a Philippine boxer who took the WBA World Flyweight Championship in a fifteen round Unanimous Decision on October 19, 1969 against Japanese boxer Hiroyuki Ebihara at the Prefectural Gymnasium, in Osaka, Japan.
 Villacampo's business manager was Lope Sarreal Jr.
 A strong puncher, he knocked out opponents in 40% of the matches he won.
James Tillis (born July 5, 1957) is a former professional boxer.
 Known as "Quick", he was known for his fast hand speed.
 Tillis challenged for the WBA world heavyweight title in 1981, but was defeated by fifteen round unanimous decision to Mike Weaver.
 Tillis was the first man to go the distance with a prime Mike Tyson in 1986.
 He holds notable wins over Ron Stander by TKO 7 in 1980, and the hard punching Earnie Shavers by ten-round decision in 1982.
 Tillis fought for the last time in 2001 at the age of 44.
Juan Nazario (born September 27, 1963 in Guaynabo, Puerto Rico) is a former professional boxer.
 During his career, which lasted from 1982 to 1993, Nazario won the WBA world lightweight title.
 His first world title challenge came in 1987 when he fought fellow Puerto Rican Edwin Rosario for the WBA belt, Rosario won the fight by an eighth round knockout.
 Nazario and Rosario fought a rematch in 1990, once again for the WBA title.
 Nazario was able to reverse the result of the first fight by beating Rosario in the eighth round to become champion.
 In his first defense Nazario challenged Pernell Whitaker for the undisputed title.
 Whitaker won the fight in the first round and Nazario never fought for a world title again.
 Nazario fought for a final time on July 10, 1993, beating Angel Cordova by unanimous decision.
Yuriy Nuzhnenko is a Ukrainian boxer who captured the vacant WBA Interim Welterweight belt on December 8, 2007 in Le Cannet, France against Frédéric Klose of France by twelve-round unanimous decision.
MacArthur "Mac" Foster (June 27, 1942 – July 19, 2010) was an American heavyweight professional boxer.
 Foster competed from 1966 to 1976, and won 30 of 36 professional bouts.
 All wins by way of knockout.
 He scored notable stoppages of heavyweight contenders such as Thad Spencer, Cleveland Williams (twice)and Zora Folley.
 Foster went the distance against a prime Muhammad Ali in April 1972, losing by fifteen round unanimous decision.
César Canchila is a boxer from Colombia who fights in the light flyweight division, where he is a former WBO Latino and WBA Fedelatin champion.
 He was born in the small town of Cereté on March 15, 1982 and currently resides in Montería.
 On July 26, 2008 Canchila captured the vacant WBA Interim Light Flyweight Title when he won a unanimous decision against the previously unbeaten Giovanni Segura in Las Vegas.
 Canchila would then lose the title in a rematch to Segura in his very next bout by 4th round TKO on March 14, 2009.
Evander Holyfield (born October 19, 1962) is an American former professional boxer who competed from 1984 to 2011.
 He reigned as the undisputed champion in both the cruiserweight and heavyweight divisions, being the first and to date only boxer in history to do so, which earned him the nickname of "The Real Deal".
 Holyfield is the only four-time world heavyweight champion, having held the WBA, WBC, IBF, and lineal titles from 1990 to 1992; the WBA, IBF, and lineal titles again from 1993 to 1994; the WBA title from 1996 to 1999; the IBF title from 1997 to 1999; and the WBA title for a fourth time from 2000 to 2001.

Question: What nationality is the boxer who went against Sean Mannion or the vacant WBA title and won over a fifteen round unanimous decision?
Answer: Jamaican