DHAKA, Bangladesh (AA) – A new study by a top Bangladeshi medical university has found that antibodies against COVID-19 diminish six months after an individual receives a booster shot, which could be helpful in deciding whether elderly or immunocompromised people need a fourth vaccine dose.

Bangabandhu Sheikh Mujib Medical University (BSMMU) recently conducted the month-long study titled ‘Hematological Parameters and Antibody Titre Six Months After Third Dose of Vaccination against SARS-CoV-2,’ in which they tested antibody levels in 223 people in Bangladesh.

Six months after they received a third COVID booster dose, the level of antibodies produced in the human body against the coronavirus was measured.

The results of the study, which were made public Monday, showed that up to 98% of the participants developed antibodies after taking two doses of the COVID vaccine, but the levels of their antibodies decreased six months after the second dose.

During the period, antibody levels decreased in 73% of the participants from 6,792 arbitrary units per milliliter (AU/mL) to 3,963 AU/mL.

Two of the patients had no antibodies six months after the second dose.

Following the third dose, antibody levels increased in the patients to 20,878 AU/mL, but after six months, the levels came down to 10,675.7 AU/mL.

Those with a history of COVID infection had increased antibody levels. No significant changes were observed in the blood parameters, including hemoglobin and platelets, said BSMMU Vice-Chancellor Md Sharfuddin Ahmed.

“The World Health Organization and the governments concerned will decide whether those receiving the booster doses should receive a fourth dose as antibody levels decline. These research results can be useful in deciding whether vaccination is needed,” he said in a statement.

An earlier study in the same research project by BSMMU showed that 98% of the 223 people had antibodies after one month of receiving their first and second doses of a COVID vaccine. Those who had previously been infected with the coronavirus had relatively more antibodies.

“However, even in this case, after six months of vaccination, the number of antibodies decreased in most cases,” the study said.

In Bangladesh, coronavirus vaccination began on Feb. 7 last year. More than 130 million people have taken their first dose of a coronavirus vaccine. Among them, more than 120 million received a second dose and more than 40 million were given a booster shot, according to BSMMU.