As Bangladesh is now administering four types of Covid vaccines without joining the trial of anyone, health experts suggest conducting a comprehensive study to know their comparative performances and the longevity of antibodies they produce.

They said some small studies have been conducted by different organisations in the country with insignificant sample size, mainly on the efficacy of AstraZeneca vaccine, but there is no study on other vaccines -- Pfizer, Moderna and Sinopharm.

The analysts think an inclusive study will help understand which vaccine is most suitable and effective in Bangladesh as the efficacy of vaccines varies from country to country and race to race.

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Besides, the analysts also said a nationwide serosurveillance also should be conducted to know how much people gained natural antibody through Covid infection and its durability as they believe a good portion of the population has already been infected with the virus.

Vaccination scenario

According to the Directorate General of Health Services (DGHS), a total of 23,167,924, people received the first dose of vaccines while 15,262,693 both doses as of September 21.

Of the dispensed 23,167,924 first shot, 7,042,743 are of AstraZeneca jabs, while 55,852 of Pfizer, 2,578,567 of Moderna and 13,490,762 of Sinopharm ones.

Of the administered second dose, some 5,402,884 people received AstraZeneca jabs while 44,621 people Pfizer, 2,390,619 people Moderna and 7,424,569 Sinopharm ones.

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Importance of vaccine study

Infectious disease expert Dr Be-Nazir Ahmed, a former director (Disease Control) at the DGHS, said usually the efficacy of any vaccine is examined during its trial. 

“But the effectiveness of any vaccine varies from country to country and race to race. So, it was necessary for our country to join the trial of different vaccines. Since no vaccine trial was conducted here, we need to understand the comparative performance of the vaccines through a large-scale post-vaccination study,” he said.

The expert said the Institute of Epidemiology, Disease Control and Research (IEDRC) should conduct a major study across the country to know the separate results of all the vaccines beings used in Bangladesh.

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He said the government has allocated enough fund for such studies, but IEDCR cannot do it due to various constraints, including manpower shortage.

“Through a widespread study, we’ll be able to know whether the vaccines can give our people necessary protection. If we find any vaccine is not working well, then we can stop collecting that particular vaccine. We’re now blindly procuring the vaccines without knowing how they are working,” Dr Be-Nazir observed.

Echoing Dr Be-Nazir, renowned scientist and Gono Bishwabidyala’s microbiology department Prof Dr Bijon Kumar Sil said though Bangladesh has been administering vaccines approved by the WHO, it is now important to know the comparative results of those by conducting a scientific study with representative samples.

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He said Pfizer and Moderna are the same type of vaccines though they need different levels of temperature for preservation while AstraZeneca and Sinopharm are totally different types of vaccines. “So, we need to see which of the four vaccines is most suitable for our country’s people through a comparative study.”

Dr Bijon said such a study will also help know which vaccine is giving greater antibodies and which one’s antibody remains for a long period.

“Preservation of vaccines at every step--from transportation to the administration--is necessary at the required temperature for maintaining their quality. For example, Pfizer vaccine jabs have to be kept at minus 20 degrees Celsius. Or else, the quality of the jabs will decline. So, a study will help us understand whether we’re properly preserving the vaccine or the quality of vaccines is declining before their inoculation,“ he opined.

READ: India to restart Covid vaccine exports to COVAX, neighbours

The expert also said most countries in the world are conducting such studies to know the comparative performance of different vaccines to revise their vaccine procurement policy.

Serosurveillance

Dr Bijon said the government should also conduct a serosurveillance in different areas across the country to understand how much people in the country already gained Covid-fighting antibodies through vaccination or natural infection.

“Many experts are saying antibodies have developed among over 70 percent people in Bangladesh through natural infections. I personally think it is over 80 percent. Otherwise, the highly transmissible Delta variant wouldn’t have come under control,” he said.

As the current virus infection rate has come down to below five percent, the expert said it is an indication that most people now have antibodies in Bangladesh.

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“But still vaccination is necessary to boost up the antibody. But if we can carry out major scientific research, then we’ll get a clear idea about the percentage of our population who have antibodies,” he opined.

According to the National Centre for Immunisation Research and Surveillance (NCIRS), serosurveillance provides estimates of antibody levels against infectious diseases and is considered the gold standard for measuring population immunity due to past infection or vaccination.

Checking elderly people’s antibodies   

Prof Muzaherul Huq, a former adviser to WHO South-East Asia region, said the study should focus on identifying the different levels of antibodies among different age groups, and among those who received vaccines and those who gained antibodies through natural infections.

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“The priority should be given to the antibody levels of elderly people. The antibody that developed through infections or vaccines can decay over phases of time. It also varies from person to person. Usually, the antibodies of elderly people can wear off fast" he opined.

Prof Muzaher said unless it is proved the antibody can protect anyone for a long time, elderly people, especially those who have comorbidities, will require a booster dose.

He also said the government should allow the private hospital to conduct antibody tests, and those that have so far not gained antibody should be given priority to get the vaccine.

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