PETALING JAYA: Malaysians have been urged to not get too complacent as a fourth wave of Covid-19 infections could strike. Medical experts warned that it could involve mutant strains of the virus that are more contagious and resistant to available vaccines. Virologist Prof Dr Sandy Loh of Universiti Nottingham Malaysia expressed fears that the mutant strains in the fourth wave could increase the number of patients in hospitals with severe Covid-19 cases. “Without vaccination, the virus will mutate in a patient with a weakened immune system,” she said yesterday. “The virus has adapted and can replicate or transmit easier. Without a sufficiently vaccinated population, herd immunity would not be achieved anytime soon as the vaccination roll-out in the country is still slow.”