6 June 2024

Subcutaneous injection of lower doses of COVID-19 vaccine generates a lower immune response than intramuscular injection, but produces fewer undesirable side effects, according to the findings of a research study by the Siriraj Institute of Clinical Research at Siriraj Hospital.

The research centre disclosed the findings today (Tuesday) of the vaccination program conducted on 210 people aged 65 years old and over, who had received two AstraZeneca vaccine shots and were given a booster dose of either Pfizer or Moderna vaccines. Subcutaneous and intramuscular injections were used on two separate groups.

One-fifth of a dose of vaccine was administered in cases of subcutaneous injection, compared to full doses for intramuscular injection.

In both cases, the findings show that the vaccines generated high levels of immune response against Omicron infection. The immune response to the Moderna vaccine was, however, higher than that of Pfizer vaccine.

The research also concludes that it is necessary for those aged at least 65 to be inoculated with a booster dose, which will protect them against being infected with the Omicron variant.

A total of 56.4 million people in Thailand, or about 81.1% of the entire population, have received at least one dose of COVID-19 vaccine, 26.6 million of whom have received their booster shots.