  Since the end of 2019, COVID-19 has significantly affected the lives of
people around the world. Towards the end of 2020, several COVID-19 vaccine
candidates with relatively high efficacy have been reported in the final phase
of clinical trials. Vaccines have been considered as critical tools for opening
up social and economic activities, thereby lessening the impact of this disease
on the society. This paper presents a simulation of COVID-19 spread using
modified Susceptible-Infected-Removed (SIR) model under vaccine intervention in
several localities of Malaysia, i.e. those cities or states with high
relatively COVID-19 cases such as Kuala Lumpur, Penang, Sabah, and Sarawak. The
results show that at different vaccine efficacy levels (0.75, 0.85, and 0.95),
the curves of active infection vary slightly, indicating that vaccines with
efficacy above 0.75 would produce the herd immunity required to level the
curves. In addition, disparity is significant between implementing or not
implementing a vaccination program. Simulation results also show that lowering
the reproduction number, R0 is necessary to keep the infection curve flat
despite vaccination. This is due to the assumption that vaccination is mostly
carried out gradually at the assumed fixed rate. The statement is based on our
simulation results with two values of R0: 1.1 and 1.2, indicative of reduction
of R0 by social distancing. The lower R0 shows a smaller peak amplitude about
half the value simulated with R0=1.2. In conclusion, the simulation model
suggests a two-pronged strategy to combat the COVID-19 pandemic in Malaysia:
vaccination and compliance with standard operating procedure issued by the
World Health Organization (e.g. social distancing).
