Vaccination is our best shot at getting out of this pandemic
It has been more than a year since coronavirus first emerged, and the global pandemic has already caused the loss of over 2.5 million lives, and disrupted the lives of billions more.
It was not long ago that the virus was only checked by the extent of restrictions we used to put on our lives. The development of a safe and effective vaccine against Covid-19 was the most pressing challenge of our time, as it was “the” exit strategy from the pandemic. In the past few months, a couple of vaccine stories made headlines around the world. Recently, the CDC reported that people who have received the full course of Covid-19 vaccines can skip the standard 14-day quarantine, although vaccinated people still wear masks, practice physical distancing, and choose safe social activities.
In Bangladesh, more than 2 million people already got their first vaccine dose after the start of nationwide Covid vaccination drive on February 7. A couple of international studies reflect that vaccines are doing wonders slowing down the virus spread and transmission of Covid infection. It means the vaccine could have a bigger impact on the pandemic, as people who are vaccinated will indirectly protect those who are not.
When a large part of a population has antiviral antibodies in their body, the virus cannot spread in that community -- commonly known as “herd immunity” or “population immunity.” The proportion of the population required to be vaccinated to achieve “herd immunity” differs among diseases. For example, in case of measles, it is 95%, in polio it is 80%.
Herd immunity can be achieved by either natural infection or by vaccination, although natural infection is not desirable, as it costs unnecessary cases and deaths among the population. Hence, vaccination is the only way out of this pandemic.
There are currently more than 60 Covid-19 vaccine candidates in clinical development, and over 170 in pre-clinical development. For each of the vaccine candidates, the age group for which the vaccine has been trialed and further recommended is important. Another essential factor is storage temperature of the vaccine, which allows easy distribution worldwide, including hard-to-reach regions. And finally, vaccine efficacy, is a paramount factor in vaccine development goals. Considering these factors, a couple of vaccines comprise the bulk of the promising vaccine portfolio around the globe.
Oxford-AstraZeneca vaccine, a vaccine developed by the University of Oxford partnered with the British-Swedish company AstraZeneca, is a viral vector vaccine that stores genetic instruction in DNA. The vaccine has been authorized for use in people aged 18 or over only. It is one of the vaccines to be stored in fridges instead of very cold temperatures.
Covishield, a version of the Oxford-AstraZeneca vaccine, is manufactured by the Serum Institute of India locally, and is currently used in Bangladesh.
Pfizer-BioNTech, a vaccine manufactured by Pfizer, Inc, and BioNTech is an mRNA vaccine that utilizes an approach of injecting a tiny fragment of viral genetic code into the body. The vaccine is not recommended for children below 16 years of age, and requires a storage temperature of -70C.
Moderna vaccine, a vaccine manufactured by ModernaTX, Inc, is an mRNA vaccine and is recommended for people aged 18 years and older. The vaccine requires a storage temperature of -20C.
Novavax, a vaccine manufactured by Novavax, Inc, is a protein-based vaccine based on recombinant nanoparticle technology. The vaccine is stable at 2C to 8C.
Janssen Vaccine, a vaccine manufactured by Janssen Pharmaceutica, a Belgium-based division of Johnson & Johnson, is a DNA based vaccine. The vaccine can be stored in regular fridge temperature.
Sputnik V, a vaccine developed by the Gamaleya Research Institute of Epidemiology, Russia, is a viral vector vaccine and can be stored at 2C to 8C.
Covaxin, manufactured by Bharat Biotech, India, is an inactivated vaccine and used a coronavirus sample, isolated by India’s National Institute of Virology.
The Sinovac, CanSino, and Sinopharm vaccines have been developed by scientists in China.
It is hard to compare vaccine efficacy, as one company’s results may vary with those of another. Also, the pattern of the trials and the duration of them at different points in the pandemic could impact vaccine efficacy. Oxford-AstraZeneca vaccine had shown 76% efficacy against symptomatic infection (meaning people who were infected with the coronavirus and felt sick) after a single dose, which increased while the second shot was delayed. The vaccine had an efficacy of 82.4% when two doses were given 12 weeks apart.
AstraZeneca vaccine is ineffective against the new variants of the coronavirus. Pfizer-BioNTech vaccine was 95% effective in people without prior infection, and >90% effective in symptomatic infection. People who have received two doses of the Pfizer-BioNTech vaccine had strong immune responses against the Kent and South African variants of coronavirus.
Moderna vaccine was 94.1% effective in people who received two doses, and 92% effective 14 days after the first dose. The Kent and South African variants of the virus do not alter the effectiveness of the Moderna vaccine. Results from the Novavax vaccine trials, involving two shots of the vaccine, found that vaccine had 95.6% efficacy against the original coronavirus, 85.6% against the Kent variant, and 60% against the South Africa variant.
A single dose of the Janssen vaccine had an efficacy of 72%, 28 days after vaccination. The vaccine had a reduced efficacy against the South Africa variant. Sputnik V vaccine is 91.6% effective against symptomatic Covid without unusual side effects.
Stopping a pandemic requires using a myriad of tools available. Getting vaccinated is one of the major steps we can take to protect ourselves from Covid-19. To this end, huge-scale manufacturing to produce billions of doses of vaccines and distribute them around the world is mandatory. Nevertheless, it is important to find out how long the protection lasts after vaccination, which is another avenue to research further.
Dr Tania Rahman is a PhD in Medicine, Dentistry, and Health Sciences, University of Melbourne, Australia, and currently teaches at the Department of Biochemistry and Molecular Biology, University of Dhaka.