[Vaccine Update]: Vaccine Facts; Oxford University Vaccine Trials Commence in India; Pregnancy Complications in COVID-19 Infected Women

Different vaccine candidates employ different engineering techniques, but whatever the approach is, the ground rules of safety and quality control remain the same.

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An effective COVID-19 vaccine or maybe herd immunity is perhaps our only hope in bringing an end to the pandemic and restoring the normalcy of life. As we near the finish lines of the race, it is essential to understand the science and challenges that follow a successful vaccine. 

The Science of COVID-19 Vaccine

Before we dive deep into the science and engineering behind a COVID-19 vaccine, let’s understand the history of the coronavirus.

Human coronaviruses were first detected in the 1960s. Coronaviruses are a broad family of viruses that typically affect the upper respiratory tract. Usually, the degree of illness is limited to mild symptoms and the common cold. However, over the past two decades, three new coronaviruses, namely, SARS coronavirus (SARS-CoV), MERS coronavirus (MERS-CoV) and the novel coronavirus SARS-CoV-2, have emerged from animal reservoirs and have wreaked havoc on humanity. 

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Needless to say, this is not the first time that scientists are working on a coronavirus vaccine. About ten years have already been dedicated to studying highly pathogenic human coronaviruses such as SARS and MERS. Scientists have leveraged past research work to fuel the development of the COVID-19 vaccine, based on what is already known to humans. Let’s have a look at some of the approaches for developing a vaccine. 

Inactivated Vaccine

An inactivated vaccine consists of an inactive virus, bacteria or pathogen that is grown in a controlled environment. The pathogenic particles cannot divide further but can be detected by the immune system to give a response. However, oftentimes, inactivated vaccination requires subsequent booster doses for lasting immunity. Improper inactivation also poses serious threats.

China’s leading vaccine candidate, CoronaVac, is an inactivated vaccine.

Live Vaccine

Live vaccines employ a weakened version of the pathogen such that an immune response can be obtained without the disease. Live vaccines have been used in case of measles, mumps, smallpox, chickenpox, among others. 

However, considerable safety has to be ensured in case of live vaccines because people with weak immune systems may succumb to the live virus. 

Genetically Engineered Vaccine

Genetic engineering or genetic modification employs biotechnology to manipulate the genetic material of the organism. The genetically engineered RNA or DNA produces copies of the S protein. Such copies cause an immune response. All in all, no infectious virus has to be handled in the process.

Many labs have manufactured genetically engineered vaccines, but no such vaccine has been authorized for human use. 

Whatever the approach be, the COVID-19 vaccine has to be manufactured factoring in extensive safety and quality measures. 

Challenges Of A Vaccine 

Past research has also highlighted some challenges that might come along while developing and producing the vaccine. Certain vaccines for SARS-CoV have produced lung complications in some people. A COVID-19 vaccine will require rigorous testing to ensure safety for the masses. This is why Russia’s fast-trialled Sputnik V vaccine met with a lot of criticism from experts in the field. 

Another critical requirement of a vaccine is to be able to render long-term protection. This is especially necessary to ensure that people do not get re-infected with the virus. Till now, only some vaccines were able to provide lifetime immunity such as the one against measles. However, some believe that our immune response to the COVID-19 virus may get compromised more quickly than we expected. If this is true, chances of reinfection will increase and perhaps one shot of vaccine won’t be enough. 

Pharmaceuticals are aiming that the vaccines provide a potent and lasting immunity against the virus. In fact, vaccines from Moderna, Oxford, among others, are showing promising results along these lines. 

An ideal vaccine should also work effectively for the different age groups like older people and children. These will be tested in the clinical trials of humans. 

The last hurdle lies in the production and distribution of the vaccine. On approval, a great deal of time will be required to produce and distribute the vaccine across the globe.  

COVISHIELD Enters Phase 2 Trials In India

The Serum Institue of India got the ball rolling as the Phase 2 trials of Oxford-Astrazeneca’s COVID-19 vaccine, Covishield, got initiated on 25th August. Six patients have been screened for an antibody test. Should the reports come negative, the patients will be inoculated with the vaccine. 

The Indian Council of Medical Research (ICMR) officially confirmed the commencement of the trials. The body is the secondary sponsor of Phase 2 and Phase 3 human clinical trials of Covishield. About 1600 people will participate in these trials. 

About 100 individuals will participate in the Phase 2 trials before commencing the phase 3 trials after ten days which will include roughly 1500 participants. Phase 2 is crucial to assess any side-effects of the vaccine.

Earlier this month, the Drug Controller General of India (DCGI) approved SII to conduct the Phase 2 and Phase 3 trials.  

Pregnancy Complications in COVID-19 Infected Women

This week, a woman in her late 20s, suffered a miscarriage due to COVID-19. The woman was in her first trimester and had contracted the virus when she was eight weeks pregnant. Four weeks later, a second test revealed that there were no traces of the virus in her nasopharyngeal tract anymore. However, five weeks after the second test, a routine test showed that her foetus was dead. 

The foetus suffered an abnormal inflammation due to the accumulation of body fluid. A study showed that the miscarriage was caused because the virus managed to travel to the womb. The virus replication was detected in the placenta cells even with no traces in the nasopharyngeal tract. 

National Institute of Research in Reproductive Health (NIRRH) stated:

To our knowledge, this is the first case demonstrating persistence of SARS-CoV-2 infection in a tissue weeks after clearance in the throat swabs… the virus not just survived in the tissue but is replicative in the placental cells.

Although this is a rare case of COVID-19-induced miscarriage, it is also not the first such case. Earlier, a woman from Switzerland gave birth to a stillborn baby in her second trimester. 

Albeit the placenta acts as a barrier against external infections, in some cases, it paves the way for the virus to replicate. In a study conducted on COVID-19 positive pregnant women, about 12% had the virus replicated on the placental cells. Scientists think that this can be attributed to the fact that placenta houses an abundant amount of S protein proteases and ACE2 receptors – a key entry point for the SARS-CoV-2 virus.  

Dr Smita Mahale, Director, NIRRH, stated:

We used single-cell RNA-seq data in placenta. Placental cells also have machinery that helps in the replication of the virus. We are still not sure why vertical transmission happens but placenta may act as an entry point for the virus.

All in all, vertical transmission is rare but has been observed worldwide. The US Centres for Disease Control and Prevention (CDC) also stated that pregnant women that have contracted the virus require intensive care to ensure the safety of the baby. 

Wadia Hospital, Mumbai and NIRRH will further study the chances of vertical transmission in pregnant women. Tests will be conducted on 100 women to check if the virus replicates on the placenta till the delivery. The Maharashtra government will also maintain records of all the COVID-19 positive pregnant women and their post-partum period of 42 days. This will help the government to strategize maternal-child care during this deadly pandemic. 


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