Amidst a rise in cases and the emergence of new variants of coronavirus, we sit down with Dr Maulik Patel, Physician and Consultant at Mediaid Healthcare LLP to answer the most frequently asked questions on the COVID-19 vaccine.
Anuja Venkatachalam
India reported 216,850 new cases of COVID-19 on Thursday – the highest-ever daily case rate since the outbreak in Wuhan last year.
Despite being a forerunner in vaccine development – with not one but two locally produced vaccines, and vaccine distribution reaching Phase 2; the sudden spike in cases has led to questions being raised about vaccine efficacy and distribution, as the government recently sanctioned the import of foreign vaccines to meet local demand.
We consulted Dr Maulik Patel, a Physician and Consultant for Emergency Medicine and Critical Care to answer your top questions on the COVID-19 vaccine.
Dr. Maulik Patel has 9 years of experience as a medical practitioner. He is the Founder of Divine Life Hospital in Gujarat. Dr. Patel completed a DNB in General Medicine from Apollo Hospital, Bangalore in 2012.
Here are your top 10 questions on the COVID-19 vaccine, answered.
1. Different vaccines have different efficacy rates. What exactly does vaccine efficacy mean?
Vaccine efficacy is the percentage reduction in disease incidence in the vaccinated group as compared to the unvaccinated group under optimal conditions during the trial. It is a measure of vaccine effectiveness. So, the higher the efficacy, the greater the burden of disease that is vaccine preventable. A vaccine with the highest efficacy and lowest cost is the most cost-effective.
1. What should we make of the many different types of vaccines?
COVID-19 vaccines are being developed using several different platforms. Some of these are traditional approaches, such as inactivated virus or live attenuated viruses, which have been used for inactivated influenza vaccines and measles vaccine, respectively. Other approaches employ newer platforms, such as recombinant proteins (used for human papillomavirus vaccines) and vectors (used for Ebola vaccines). Some platforms, such as RNA and DNA vaccines, have never been employed in a licensed vaccine.
The choice between these COVID-19 vaccines is based on availability. They have not been compared directly, so comparative efficacy is unknown. However, they are all highly effective and substantially reduce the risk of COVID-19, especially severe or critical cases of the disease.
1. There are reported cases of people testing positive even after receiving their vaccine shots. What is the point of taking the vaccine, if I can still test positive?
Even when fully vaccinated, you could get COVID and spread it to others. As with any vaccine, it is possible that even people who have received both doses of the vaccine could get infected with COVID. However, this is far less likely if compared to people who have not been vaccinated. Clinical trials and empirical studies have shown that COVID-19 vaccines are very effective at preventing severe infections of the disease.
It also takes 2-3 weeks after your second dose to build an adequate immune response. It is therefore very important to continue to adopt COVID preventive measures even after taking the vaccine.
1. Most vaccines have two doses but the gap between two doses is variable, and often altered. Why is this changing and what is best for me?
For vaccines that are given in two doses, the second dose should be given as close to the recommended interval as possible but not earlier than recommended.
If necessary, the second dose can be scheduled for up to six weeks (42 days) after the first dose. If the second dose is not given within this time frame, it should be given as soon as is feasible.
The efficacy of administering vaccines outside of the recommended time frames is uncertain, although with some vaccines, using longer intervals has been associated with higher antibody response.
The schedule is being adjusted based on new data from Phase 3 of the trial that is telling us more about the effectiveness of vaccine response as it is being studied further.
The ideal time to take the second dose, however, remains to be between 4-6 weeks of taking the first dose.
1. Should the development of blood clots reported with several vaccines be a cause for concern?
Some vaccines may be associated with an extremely small risk of unusual types of thrombotic events associated with thrombocytopenia. Because of the rarity of these events and the potential severity of COVID-19, the European Medicines Agency (EMA) have concluded that the overall benefits of the vaccine continue to outweigh its risks.
The World Health Organization has also stated that a causal relationship between the two, while plausible, has not been confirmed.
Some countries have decided to suspend use of these vaccines until further evidence is available, while others have limited the vaccine to individuals over a certain age (eg, over 60 years old in Germany, over 55 years old in Canada) who are at a higher risk of this syndrome.
Most incidents have occurred within 14 days of receiving the first dose and among people under the age of 60 years. However, clear risk factors have not been identified. Some experts have suggested that these events could be related to vaccine-induced autoantibodies directed against a PF4 platelet antigen, similar to those associated with heparin-induced thrombocytopenia (HIT).
Overall, there does not appear to be an association between the COVID-19 vaccine and thromboembolic disorders overall, and more importantly, the rate of thromboembolic events following vaccination is lower than its rate in the general population.
1. The Johnson & Johnson vaccine is only one dose. Why should I take two doses of Astrazeneca or Pfizer when I can get only one of Johnson & Johnson?
The Johnson & Johnson vaccine has currently been stalled in the United States pending further investigation into a possible side effect.
The vaccine is based on a replication-incompetent adenovirus 26 vector that expresses a stabilized spike protein. It is given intramuscularly as a single dose but is also being evaluated in two doses taken 56 days apart.
Phases I and II of the trial showed high rates of neutralizing and binding antibodies after a single vaccine dose in healthy individuals aged between 18 and 85 years, but they were slightly lower than responses to convalescent plasma. A second vaccine dose was evaluated in a subset of participants, and this resulted in an increase in neutralizing titers.
Whether you get to choose a vaccine is based on availability and restrictions in your region.
1. How did COVID vaccine development take such a short time, when it typically takes decades? Isn’t it unusual?
Vaccine development for SARS-CoV-1 and MERS-CoV paved the way for the rapid development of COVID-19 vaccines.
Pre-clinical studies were already completed for SARS-CoV-1 vaccines, and two vaccines were evaluated in small human trials; however, further work was halted as infections were eliminated. Additionally, for COVID-19 vaccines, there has been a seamless transition between phases.
Nevertheless, the safety criteria for vaccine development have remained stringent. Data safety and monitoring committees (DSMCs) composed of independent vaccine experts are assessing adverse events that are reported in each phase of the clinical trial and in subsequent phases.
1. Will COVID vaccines last a lifetime or will we need to take seasonal shots?
Several SARS-CoV-2 variants with a potential for immune escape have been identified, which is a cause for concern. Data on whether vaccine-induced immunity can protect against these variants is currently limited. Based on preliminary, largely unpublished reports from efficacy trials and immunogenicity studies, COVID-19 vaccines likely retain efficacy against some of these variants. However, further research is required at this time.
1. What is the point of mass vaccination programs if immunity is time-bound?
Since most vaccine-preventable diseases are transmitted from person-to-person, vaccination not only protects the recipient but also indirectly protects others who cannot be vaccinated or do not respond to vaccines adequately. This is called “herd immunity”. Mass vaccination will prevent waves of infection as seen in the COVID-19 pandemic.
1. How can I be sure if the vaccine I get will protect me from variants? If it doesn’t, I see little benefit.
Based on preliminary, largely unpublished reports from efficacy trials and immunogenicity studies, COVID-19 vaccines likely retain efficacy against some of the variants.
There is evidence that plasma from participants who received the COVID-19 vaccine retained neutralizing activity against the B.1.351 variant, although at titers lower than for the wild-type virus.
Several COVID-19 vaccines have demonstrated efficacy in preventing symptomatic COVID-19 patients. New data particularly from mRNA vaccines suggest that vaccination reduces asymptomatic as well as symptomatic infections, and are therefore effective in curbing transmission.
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