The Department of Medical Services has rescheduled vaccinations for two at-risk groups at Bang Sue Grand Station after they turned up in droves on Thursday and failed to observe proper social distancing.
Many decided to go home after seeing the crowd lining up for Covid-19 jabs out of concern that they would catch the virus while waiting for their shots.
Thursday was the first day that the elderly aged 60 and over, people who weigh more than 100 kilogrammes and women at least 12-week pregnant could walk in at Bang Sue Grand Station for their first shots of the AstraZeneca vaccine.
Because of the large crowd, the department has rescheduled vaccination times for people who weigh over 100kg and pregnant women.
They can receive their vaccinations from 1pm to 5pm while the time slot for the elderly remains unchanged at 9am to 5pm. Jabs for these three groups are being offered until the end of the month.
Earlier, walk-in inoculations were offered to people aged 75 and above and for those aged 65 years and older who secured appointments mostly via mobile phone network providers.
City Hall spokesman Pongsakorn Kwanmuang said the Bangkok Metropolitan Administration (BMA) plans to inoculate at least 50% of the elderly by the end of this month.
However, as the number of elderly receiving vaccines is in decline, City Hall has decided to give shots to those living in at-risk zones during this campaign too, he said.
The elderly can register for a vaccination with the Thai Ruam Jai programme, but for those who are unable to do so, City Hall Comprehensive Covid-19 Response teams are making house calls to give jabs and Covid-19 antigen tests.
Mr Pongsakorn said City Hall has no plans at this stage to mix Sinovac and AstraZeneca vaccines and the vaccine to be distributed remains AstraZeneca.
He said it is difficult to predict when Covid-19 infections in Bangkok will peak, noting that there are two factors at play -- the vaccination rate and the efficacy of lockdown measures.
Dr Suksan Kittisupakorn, director of City Hall's Medical Office, said the Thai Ruam Jai vaccination programme for people aged 18-59 has been suspended due to limited vaccine supply.
He said this week's rollout, from July 22-26, is for people who booked their first jabs on June 19-23. Those with bookings from June 24 onward will be notified when a fresh batch of the vaccine is available.