Lt Col Nazmul Huda Khan :
As a part of the containment measures of Covid-19, Bangladesh has so far conducted vaccination programme for the all strata of population from urban to rural, city to slum dwellers, university to school children, immigrants, both male and female including transgender through Surokkha apps and spot registration too. Bangladesh began the administration of COVID-19 vaccines on 27 January 2021 while mass vaccination started on 7 February 2021. Since then, about 75 million people have been vaccinated either single or two doses provisioning WHO approved vaccines e.g. Pfizer, Moderna, Oxford – AstraZeneca and Sinopharm without significant side effects and complication. Now the government has decided to implement provisioning booster dose to the eligible persons following WHO, CDC and National advisory committee guidelines that have been inaugurated on last 19th December 2021.
Booster simply just as another dose of a vaccine we received. The concept of booster is to prolong protective immunity of an individual. Globally and in our country too, children receive routine vaccinations including boosters as a part of protective measure from different ailments such as tuberculosis, tetanus, diphtheria, mumps, measles and rubella etc.
Corona viruses while adapting to their new human hosts are prone to genetic evolution with the development of mutations over time resulting in mutant variants that may have different characteristics than its ancestral strains. Several variants have been described variants of concern (VOCs) by the WHO, according to their impact on global public health such as Alfa, Beta, Delta, Gamma and Omicron etc. Vaccines have been formulated and invented on the basis of prevention of spike protein invasion. But Corona virus is continuously changing its spike proteins for its survival through mutation. No vaccine invented so far is claiming to be fully protective. So, booster shot is recommended due to concern that the effectiveness of the vaccine decreases over time and may not protect against a new strain.
There are several reasons why COVID-19 vaccine booster doses may be needed. Amongst those, few are -waning protection against infection or disease, in particular severe disease over time; reduced protection against different variants and inadequate protection from the currently recommended primary series for some risk groups. The rationale for booster doses may differ by vaccine product, epidemiological setting, risk group and vaccine coverage rates.
The decision to recommend a booster dose is complex and requires a consideration of national strategic and programmatic aspects and importantly an assessment of the prioritization of limited vaccine supply beyond clinical and epidemiological data. In this context, prioritization should be given to the prevention of severe disease. Necessity can be grouped into the following categories:
– Breakthrough cases and disease severity by age
– Co-morbidity
– Risk groups and exposure
– Type of vaccine and time since vaccination
– Evidence from immunological studies assessing antibodies over time
– The context of variants of concern (VOCs)
– Effectiveness and duration of protection of primary series vaccine
– Homologous versus heterologous boosters
– Needs in previously infected individuals
– Specification and prioritization of high-risk populations.
– Safety and reactogenicity etc.
The CDC recommends that the people aged 65 years and older, residents aged 18 years and older in long-term care settings and people aged 50-64 years with underlying medical conditions should receive a booster shot at least six months after receiving their second dose. They have suggested categorically providing booster to all healthcare workers, police members, fire services personnel, teachers and school staffs, food handlers, transport workers, factory laborers, grocery sellers and other front liners in their guideline. But they have put emphasis to confirm the rate of infectivity, severity of disease, variant of concerns prevailed, risk of exposure, types and effectiveness of vaccines adopted, presence or absence of comorbidity amongst others. Bangladesh has decided to provide booster dose to people aged 60 years and above, health care workers, members of law enforcing agencies and other front line fighters.
According to WHO, at least 126 countries worldwide have already issued recommendations on booster or additional vaccination and more than 120 have started programmatic implementation. The most commonly prioritized target populations for booster doses are older adults, health workers and immunocompromised.
Research findings from booster shots given to adults have shown that a shot of Pfizer vaccine has improved immunity and has offered protection from severe illness among people over the age of 60. It has been also revealed that protection against infection provided from 10 days after a booster dose was four times higher than after two doses. Booster dose has proven to reduce infection by 11 times and severity of disease by 20 times in USA.
Now the queries have been raised, whether other types of shot can be used than that of primary series; so-called “mixing and matching” of vaccines (a first dose of Oxford-AstraZeneca followed by a second dose of Moderna or Pfizer for example). This kind of “mix and matching” method has been used in Europe and other places, particularly when there were supply issues. There have been studies suggesting this approach-with one dose of AstraZeneca’s vaccine and one dose of Pfizer’s vaccine-may even offer more vigorous protection. Different studies in US showed that, those who received the J &J vaccine for primary vaccination had a 33 fold rise in antibodies after the Pfizer booster and 56 fold increase after the Moderna booster. So, going with the same vaccine type for booster is fine. Mixing and matching is perfect too. Joint committee on vaccine and immunization of UK has recommended Oxford – AstraZeneca jab to be utilized as booster to immunocompromised personnel. China is also using Sinopharm as 3rd dose for Comorbid, aged and immunocompromised individual. UAE is also provisioning Sinopharm as booster.
There found no significant side effects of booster doses. According to the FDA, the most commonly reported side effects of a booster dose included pain, redness, and swelling at the injection site; fatigue; headache; chills; and muscle or joint pain.
COVID-19 breakthrough infections are being reported even in fully vaccinated people. While not complying with COVID appropriate behavior does play a role, there is no denying the fact that the latest variant Omicron has played their part in reinfections, same is fact for other variants of concerns too. The newer Omicron can spread 70 times faster than devastating Delta variant. In this context the demand for a booster shot has been increased.
Booster shots are for people who are fully vaccinated. It will not provide 100% protection. They are administered to provide them with an extra layer of protection against the disease. But keep in mind that the immune protection offered by the primary vaccination plus the booster may vary from person to person. What may be the optimal booster shot for someone may not be the effective one for another. So, even after boosted, let us try to maintain other COVID-19 precautions as much we can such as face mask use and social distancing as long as the virus remains widespread around us. So bottom line is that protection offered by the primary vaccination plus the booster will depend on how many other precautions we are layering on as well.
(Lt Col Nazmul is Assistant Director, Kurmitola General Hospital).
