The Omicron subvariants BA.4 and BA.5 are increasingly reported in multiple countries, including Thailand. How dangerous are these variants, and how should we prepare to prevent infection?

How Dangerous Are Omicron BA.4 and BA.5?

BA.4 and BA.5 carry the L452R mutation in the spike protein, potentially making them more transmissible than earlier Omicron subvariants (e.g., BA.2) and enabling faster replication in lung tissue. These subvariants may replace BA.2 due to their ability to evade immunity from prior infections, meaning individuals previously infected with BA.1 or BA.2 can be reinfected with BA.4/BA.5.

How to Protect Against BA.4 and BA.5?

1. Vaccination:

   • Vaccines remain critical for preventing severe illness and death.

   • Booster doses (especially mRNA vaccines) enhance immunity, particularly for high-risk groups (Group 608), who should receive a booster 4 months after their third dose.

2. Preventive Measures:

   • Continue handwashing, social distancing, and mask-wearing in crowded/poorly ventilated areas, even as Thailand relaxes mask mandates.