It comes after some public figures revealed they tested positive despite taking their first dose of the vaccine.
Disaster Management and Relief Secretary Md Mohsin tested positive for Covid-19 twelve days after receiving his first dose of the Oxford-AstraZeneca vaccine that is being rolled out in Bangladesh.
Bangladesh national hockey team coach Mahbub Harun tested positive with 65% infection in lungs within a week of taking his first dose of the vaccine.
Renowned film director Kazi Hayat and his wife also tested positive within just six days of receiving their first dose of the vaccine.
These prominent cases combined with the current upswing in infections as well as deaths to fuel questions over the efficacy of the vaccine – to the point that some began to link testing positive to having taken the vaccine.
Also read: Experts fear Bangladesh may see fresh wave of Covid-19
Why you may still test positive
While some vaccines stop people from getting infected, providing what is called sterilising immunity, others are aimed at preventing symptomatic disease – you may still get infected, but the immune response triggered by the vaccine will fight off severe disease. The Covid-19 vaccines fall in the latter category.
The DGHS statement rested on the fact that no-one in Bangladesh has yet received the recommended two doses of the vaccine in the first place.
“One has to wait a minimum of two weeks after taking the second shot to get the maximum immunity from the Covishield vaccine used in the Covid-19 vaccination drive," it said.
The Oxford-AstraZeneca vaccine is being branded as Covishield by its licensed Indian manufacturer the Serum Institute of India (SII).
"The risk of being infected with Covid-19 stays the same if the health guidelines are not maintained properly during this waiting period (between the first and second doses)."
Also read: Covid-19 in Bangladesh: 95,675 get vaccine shot in 24 hours
Difference between immune response and full protection
"It is true that the immune response starts after taking the jab but protection comes only once a person completes the recommended dosage," Dr Be-Nazir Ahmed, former director (disease control) of the DGHS, told UNB on Monday evening.
He also said, "Vaccination means one has to complete taking all the doses of a vaccine to get the complete protection."
"As the AstraZenecca Covid-19 vaccine is a two-shot vaccine, one cannot claim to be infected by Covid-19 despite vaccination before taking both the shots," he added.
To measure the efficacy of a vaccine, completing all the doses is a precondition, Dr Be-Nazir said.
"The virus can enter one's body before taking the shots and be in incubation period, without showing the symptoms. During this period if one takes the vaccine and then tests positive, that would actually be due to a prior exposure. As the virus was already in the body and the immune response triggered by the shot hadn’t started yet, the person would end up with Covid-19,” said the former director of DGHS.
It may be mentioned that Covid-19 is the name given to the disease caused by infection with the novel coronavirus.
Dr Be-Nazir pointed out that it is being advised across the world to keep maintaining the non-pharmaceutical health guidelines alongside vaccination drives now underway in a number of countries.
"The AstraZeneca Covid-19 vaccine was claimed to have an efficacy of 60%-70%, meaning caution has to be maintained even after taking the two shots,” he reminded.
"However, vaccination is important and logical as it lowers the risk of severe disease or death from COVID-19. To protect your life you must take the vaccine," he concluded.
Covid-19 vaccination drive in Bangladesh
Bangladesh vaccinated 87,860 more people against Covid-19 in the past 24 hours.
Directorate General of Health Services (DGHS) on Monday reported vaccinating 50,244 men and 37,616 women with the Oxford-AstraZeneca vaccine in the said period.
With this, 4,485,954 people in total received the first dose of the Oxford-AstraZeneca vaccine until Monday. The second dose has to be taken between 8 and 12 weeks of the first one.
Bangladesh launched its nationwide Covid-19 vaccination drive on February 7.
Around 44 lakh people have received the Covid-19 shot from January 27, when some people received the vaccine on a pilot basis, to March 14.
The government is providing the vaccine for free. It signed an agreement with India's Serum Institute for acquiring 30 million doses of the vaccine.
The institute will provide 5 million doses every month between January and June.
Those who are 40 or above can register for getting the jab at www.surokkha.gov.bd as the on-spot registration system has been revoked.
Also read: Alarming Covid surge in Bangladesh, 26 more die
Covid-19 situation in Bangladesh
Amid the fear of a fresh wave of Covid-19 and detection of UK variant of the virus, Bangladesh witnessed a sharp increase in the number of deaths and new cases on Monday.
The deadly virus claimed 26 more lives and infected 1,773 more in the last 24 hours till Monday morning.
With the latest figures, the Covid-19 fatalities climbed to 8,571 while the total infections to 559,168, according to a handout of the Directorate General of Health Services (DGHS).
The daily infection rate jumped to 9.48 percent from 7.15 percent on Sunday.
The virus infection rate had come down to below 5% on January 19 last. It even had come down below 3 percent. However, the infection rate soared again on Tuesday last as it increased to 5.13%.
The infection rate was 5.98% on Wednesday while 5.82 percent on Thursday, 6.62% on Friday and 6.26% on Saturday.
Bangladesh reported its first cases on March 8, 2020 and the first death on March 18 in the same year.
Authorities have so far tested 4,283,246 samples, including 18,695 in the past 24 hours.