The National Health Security Office (NHSO) board has approved a proposal to include in its health coverage laboratory tests to diagnose and treat blood clots related to Covid-19 vaccination.

NHSO Secretary-General Jadej Thammatacharee said on Tuesday while the chance of jab recipients suffering from "vaccine-induced immune thrombotic thrombocytopenia", or VITT, is very low, the NHSO board had decided to expand coverage to build up public confidence in the vaccines.

According to Dr Jadej, VITT syndrome occurs in between 1:125,000 and 1:1,000,000 recipients. Recipients experiencing severe or unusual symptoms four to 30 days after vaccination are advised to seek medical attention.

Symptoms include severe headaches, weakness in the limbs, slurred speech, breathing difficulty, abdominal pain, leg pain, chest pain and swelling of the legs. He said medical expenses for diagnosis and treatment will be covered by the NHSO.

Meanwhile, health authorities in Rayong said they are looking into the case of a policeman who suffered stroke-like symptoms a few hours after receiving a Sinovac shot on June 2.

Chakkarin Pramongkhet, an official from NHSO's Zone 6, said the case involving Pol Snr Sgt Maj Sitthichai Khlaipan was the province's fifth initially found to be linked to vaccination.

He said compensation will be paid as soon as the office receives a medical report from Rayong Hospital where Pol Snr Sgt Maj Sitthichai was treated.

He also added that compensation had been paid to recipients in the other four cases.

The officer from Chamao police station reportedly developed symptoms a few hours after receiving the shot.

They included vomiting, chest pain and weakness on the left side of his body.