RT Journal Article SR Electronic T1 Epidemiological comparison of the first and second waves of the COVID-19 pandemic in Nigeria, February 2020–April 2021 JF BMJ Global Health JO BMJ Global Health FD BMJ Publishing Group Ltd SP e007076 DO 10.1136/bmjgh-2021-007076 VO 6 IS 11 A1 Oluwatosin Wuraola Akande A1 Kelly Osezele Elimian A1 Ehimario Igumbor A1 Lauryn Dunkwu A1 Chijioke Kaduru A1 Olubunmi Omowunmi Olopha A1 Dabri Olohije Ohanu A1 Lilian Nwozor A1 Emmanuel Agogo A1 Olusola Aruna A1 Muhammad Shakir Balogun A1 Olaolu Aderinola A1 Anthony Ahumibe A1 Chinedu Arinze A1 Sikiru Olanrewaju Badaru A1 William Nwachukwu A1 Augustine Olajide Dada A1 Cyril Erameh A1 Khadeejah Hamza A1 Tarik Benjamin Mohammed A1 Nnaemeka Ndodo A1 Celestina Obiekea A1 Chinenye Ofoegbunam A1 Oladipo Ogunbode A1 Cornelius Ohonsi A1 Ekaete Alice Tobin A1 Rimamdeyati Yashe A1 Afolabi Adekaiyaoja A1 Michael C. Asuzu A1 Rosemary Ajuma Audu A1 Muhammad Bashir Bello A1 Shaibu Oricha Bello A1 Yusuf Yahaya Deeni A1 Yahya Disu A1 Gbenga Joseph A1 Chidiebere Ezeokafor A1 Zaiyad Garba Habib A1 Christian Ibeh A1 Ifeanyi Franklin Ike A1 Emem Iwara A1 Rejoice Kudirat Luka-Lawal A1 Geoffrey Namara A1 Tochi Okwor A1 Lois Olajide A1 Oluwafunke Olufemi Ilesanmi A1 Solomon Omonigho A1 Ferdinand Oyiri A1 Koubagnine Takpa A1 Nkem Usha Ugbogulu A1 Priscilla Ibekwe A1 John Oladejo A1 Elsie Ilori A1 Chinwe Lucia Ochu A1 Chikwe Ihekweazu YR 2021 UL http://gh.bmj.com/content/6/11/e007076.abstract AB Background With reports of surges in COVID-19 case numbers across over 50 countries, country-level epidemiological analysis is required to inform context-appropriate response strategies for containment and mitigation of the outbreak. We aimed to compare the epidemiological features of the first and second waves of COVID-19 in Nigeria.Methods We conducted a retrospective analysis of the Surveillance Outbreak Response Management and Analysis System data of the first and second epidemiological waves, which were between 27 February and 24 October 2020, and 25 October 2020 to 3 April 2021, respectively. Descriptive statistical measures including frequencies and percentages, test positivity rate (TPR), cumulative incidence (CI) and case fatality rates (CFRs) were compared. A p value of <0.05 was considered statistically significant. All statistical analyses were carried out in STATA V.13.Results There were 802 143 tests recorded during the study period (362 550 and 439 593 in the first and second waves, respectively). Of these, 66 121 (18.2%) and 91 644 (20.8%) tested positive in the first and second waves, respectively. There was a 21.3% increase in the number of tests conducted in the second wave with TPR increasing by 14.3%. CI during the first and second waves were 30.3/100 000 and 42.0/100 000 respectively. During the second wave, confirmed COVID-19 cases increased among females and people 30 years old or younger and decreased among urban residents and individuals with travel history within 14 days of sample collection (p value <0.001). Most confirmed cases were asymptomatic at diagnosis during both waves: 74.9% in the first wave; 79.7% in the second wave. CFR decreased during the second wave (0.7%) compared with the first wave (1.8%).Conclusion Nigeria experienced a larger but less severe second wave of COVID-19. Continued implementation of public health and social measures is needed to mitigate the resurgence of another wave.Data are available on reasonable request. Data may be made available on request, subject to compliance with the Nigeria Centre for Disease Control (NCDC) data sharing policy.