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Dhaka Tribune

Everything you wanted to know about the vaccine but were afraid to ask

To fight against Covid-19, we must first arm ourselves with the correct information

Update : 04 Apr 2021, 04:12 PM

 I lost my mother to Covid in December. She rarely went out, managed her business and family affairs from home, and did not attend any social gatherings. There was just this one day when she had stepped out to see her ailing brother who, sadly, also passed away from Covid four days after her. 

As a daughter and a doctor, I live with tremendous guilt that I could not protect her, especially when the vaccine was so close. I myself had mild Covid last year, took my first vaccine shot in March, and still adhere to social distancing guidelines. 

Why? Because I am aware that I can again be an asymptomatic carrier and transmit the virus to others. 

The recent rise in cases began exactly a year after the first Covid patient was detected in the country, and as of March 31, we are setting new records of cases and deaths every single day. Despite a clear indication of another surge, our health care facilities are once again unprepared to cope with the sudden onslaught of new infections. 

The government just imposed a circuit-breaker lockdown. It is a timely decision to break the vicious cycle of transmission. 

There is general confusion among people regarding the sudden spike in infection and doubts are creeping in about the efficacy of the vaccine. We also do not know whether a new variant is responsible for this new outbreak or not. No one has the answers yet, but we can check some facts:

  • Till date, 5.37 million have been vaccinated. It may sound like a lot, but it only represents 3.3% of our population and these people received just one dose of the vaccine when the full recommended dose is two shots 
  • The vaccine is NOT a silver bullet 
  • And, finally, everyone is flouting the health guidelines

Let me take this opportunity to elaborate on how vaccinations reinforced with strict health guidelines can eventually bend the curve as it has done in some other countries.  

So, how do vaccines actually work?

Vaccines are developed using the principle of mimicking the body’s natural immune response to a pathogen. Weakened parts of a disease-causing pathogen (antigen) are inoculated to trigger the immune system to produce protective cells, antibodies, and memory cells against that antigen. 

Some vaccines require multiple doses or booster doses to produce long-lasting antibodies and memory cells to train the body to fight against specific diseases. 

What is ‘effective immunity’ and ‘sterilizing immunity?’

The holy grail for vaccine researchers is to develop vaccines that can provide 100% protection against infection. This is known as “sterilizing immunity” where immunity is strong enough to inhibit a pathogen from entering and replicating in the cells. Even though this is rarely achieved, there are vaccines like the MMR and polio that are more than 90% effective against the diseases.  

Majority of vaccines trigger “effective immunity,” where pathogens can enter the body’s cells and replicate, but will be stopped from developing serious illness. However, vaccinated people can still catch a virus, remain asymptomatic, and unknowingly transmit it to others. 

The approved Covid-19 vaccines’ efficacy is assessed so far on the criteria of preventing disease symptoms and not necessarily on their ability to prevent transmission. So, persons vaccinated with one dose or those who have been infected once with Covid-19 can potentially still get reinfected, be an asymptomatic carrier, and pass the virus to others. New data is coming in about the Pfizer and Moderna vaccines’ ability to inhibit transmission of the virus. 

What does it mean to be fully vaccinated against Covid and what are ‘breakthrough cases?’

A person who has had both doses of the vaccine is considered to be fully vaccinated. Any person developing the illness any time two weeks after receiving the second dose of vaccine is known as a breakthrough case. 

The two-week mark is important as it gives the body time to develop immunity. Breakthrough cases are an expected outcome of any vaccination process, particularly when the virus is widely circulating in the community and new variants are emerging. 

Countries like the US and the UK are reporting rare breakthrough cases, but their health officials re-affirm that these are mild cases, and the vaccination prevents hospitalization or serious illness. 

An interesting finding by Israeli scientists published in Bloomberg Opinion suggests that it is the IgA type of antibody in the nasal passages and respiratory tract that stops the virus. Much has been written about the IgG antibodies that develop right after the vaccination and a high level of IgG does give protection but not as effectively as IgA antibodies. 

One might argue as to why I am getting into such technical details -- it is just to highlight that we are still gathering data and do not have the full picture yet.  

Why do breakthrough cases occur? 

A person is most susceptible to infection in the immediate aftermath of vaccination due to incompletely established immunity. Immune system response depends on the health status of a person and it may take two to 12 weeks to produce immunity. 

The other factor to consider is that the vaccine was developed from a particular strain and the new strains might be resistant to the vaccine. All these considerations are under further study and experts suggest that as more people get vaccinated, emergence of breakthrough cases will disappear. 

In the case of Bangladesh, breakthrough cases are not even a possibility as only three out of 100 people in the country have received just one dose of the vaccine. Nevertheless, it is a good reminder that even vaccinated people are not invincible and wearing masks with other mitigation guidelines must be continued.

How would we compare AstraZeneca vaccine to Pfizer or Moderna?

Pfizer and Moderna are both over 94% effective upon full immunization whereas AstraZeneca vaccines are 76% effective against symptomatic Covid and 100% effective against severe or critical hospitalization cases. 

Unfortunately, AstraZeneca has run into many controversies since the beginning -- confusion regarding its efficacy rate, the side effects of blood clots and low platelet count in some European recipients, and South Africa halting its rollout due to its ineffectiveness against their new variant. 

Irrespective of these issues, the benefits of the AstraZeneca vaccine outweigh the risks, especially for countries like Bangladesh. The storage requirements are less rigorous, it is cheaper, thus making it the vaccine of choice for poorer countries, and a study has shown that an interval of 12 weeks between the two doses triggered long-lived immunity. 

Bangladesh invested to procure 30 million doses of this vaccine from the Serum Institute of India and till now has received 7 million doses. The government took the policy of initially vaccinating a larger number of people with a single dose to protect a larger group of people than vaccinating half the number of individuals with two doses in the short term.

India’s recent suspension on exporting the vaccine may hamper the vaccination roll out and the government is now looking at the Johnson and Johnson vaccine. This vaccine is 66% effective and requires a single dose and can be stored in a normal refrigerator, but it might only be available from September.

Is there a success story of the vaccination roll out?

Israel has led the world in the vaccination program. 55.5% of their population is now fully vaccinated with two doses of the Pfizer vaccine which includes 84% of those over 70. The country is fully open to its people since severe Covid cases and deaths have declined rapidly. 

Chart 1 / Source: 

Chart 1 shows the percentage of people fully vaccinated against Covid in different countries and Bangladesh does not fall under this category yet.

Chart 2 / Source: 

Chart 2 shows the percentage of people that received a single shot. Only 3.3% of Bangladeshis have received a single dose of the vaccine.

Chart 3 / Source:

Chart 3 shows the total number of vaccines administered in different countries. Bangladesh’s number looks decent, but we still need at least 218 million doses to cover 70% of 160 million people.

The last two week’s alarming trend of infection and death rate indicates that we are in the midst of an explosive community transmission phase. Whether it is a new strain or the UK strain or the South African strain remains to be seen. 

Experts focus on several parameters to flag the situation of any country -- the trend of critical cases, hospitalization and deaths, the level of virus transmission or new infections, and the total number of people fully vaccinated against the disease. 

Since the country is hitting new records every day, it is currently identified as a disease hot spot, and borders are again closing on us. People must absolutely go back to maintaining the social distancing guidelines, wear masks at all times, stop any kind of indoor or even outdoor social gathering. 

It only took us two months to go from an average of 350 daily new cases to over 7,000 cases. We can only become complacent when enough people are vaccinated around us to stop the transmission. 

Also, this is a new disease, any data related to vaccination and the immunity it produces are only at best three months old, so the story will continue to unfold before anything can be fully established. 

So far, masks and social distancing have consistently worked in bending the curve, and we must adhere to those until it is safe for all of us.  

Dr Maliha Mannan Ahmed is the Founder and Executive Director of Organikare. She has an MBBS, MBA, and a Master’s in Health Care Leadership. 

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