OBJECTIVES: This study aimed to develop susceptible-exposed-infectious-recovered-vaccinated (SEIRV) models to examine the effects of vaccination on coronavirus disease 2019 (COVID-19) case trends in Malaysia during Phase 3 of the National COVID-19 Immunization Program amidst the Delta outbreak. METHODS: SEIRV models were developed and validated using COVID-19 case and vaccination data from the Ministry of Health, Malaysia, from June 21, 2021 to July 21, 2021 to generate forecasts of COVID-19 cases from July 22, 2021 to December 31, 2021. Three scenarios were examined to measure the effects of vaccination on COVID-19 case trends. Scenarios 1 and 2 represented the trends taking into account the earliest and latest possible times of achieving full vaccination for 80% of the adult population by October 31, 2021 and December 31, 2021, respectively. Scenario 3 described a scenario without vaccination for comparison. RESULTS: In scenario 1, forecasted cases peaked on August 28, 2021, which was close to the peak of observed cases on August 26, 2021. The observed peak was 20.27% higher than in scenario 1 and 10.37% lower than in scenario 2. The cumulative observed cases from July 22, 2021 to December 31, 2021 were 13.29% higher than in scenario 1 and 55.19% lower than in scenario 2. The daily COVID-19 case trends closely mirrored the forecast of COVID-19 cases in scenario 1 (best-case scenario). CONCLUSIONS Our study demonstrated that COVID-19 vaccination reduced COVID-19 case trends during the Delta outbreak. The compartmental models developed assisted in the management and control of the COVID-19 pandemic in Malaysia.

Studies have shown that parents and peers are among the dominant factors that contribute to smoking initiation among non-smoking adolescents. The paucity of this information in Malaysia warrants a longitudinal study to determine the actual factors associated smoking initiation. The study aims to address the gaps in our knowledge on the factors that associated with smoking initiation among non-smoking school-going adolescents. We carried out a longitudinal study among non-smoking secondary school-going adolescents in Kota Tinggi district, Johor. A representative sample of 1682 was selected via multi-stage sampling and respondents were followed-up for a period of one year. A pre-validated questionnaire was used to collect data from the selected respondents and multivariable logistic regression was employed to determine the factors associated with smoking initiation among non-smoking school-going adolescents. Approximately 1 in 10 non-smoking school-going adolescents-initiated smoking at the end of follow-up. Having peers and a father who smokes were significantly associated with smoking in univariate analysis, similarly relationship was also observed in multivariable analysis between parents who smoked with smoking initiation after the effect of other independent variables were controlled (Adjusted relative risk: 1.81, 95% CI 1.06-2.95). The study revealed that parental influence was more dominant than peer influence with regards to smoking initiation. Therefore, intervention programmes should involve parents/guardians to enhance their chances of success and reduce the incidence of smoking among non-smoking school-going adolescents.