The What and When of Covid 19 Vaccines

The pandemic is on it’s second peak and the entire country in a state of trepidation. Many different types of vaccines have been developed and are available, now, for public use. Many vaccines are still undergoing research and will be available shortly.

With so many options available, and so much having been said about the vaccines, it can be intimidating and confusing for anyone to understand the implications of the various vaccines available to us.

The vaccines differ either on the basis of:

  1. Their basic content (Viral vector; Protein or RNA based)
  2. Their route of administration (IM; Oral or Nasal).
Categories of the vaccines, based on their vectors

Currently, Covishield and Covaxin are available for general use in India. The consignment for Sputnik V vaccine has already landed in Hyderabad and will be available shortly. According to the reports, Pfizer maybe available to us by July.

Here, is a short summary on the comparison between the most talked about vaccine options. All these are available for use through the intramuscular route.


CoviShield (AstraZenica)Covaxin (Bharat Biotech)Pfizer (BioNTech)Moderna (mRNA-1273)Jhonson & Jhonson (Janssen)Sputnik V
Vector for vaccineCommon cold virus, obtained from chimpanzee (Adenovirus)Uses a weakened viral strain from chimpanzee to boost the antibody formationGenetic material of COVID virus is introduced into the body and teaches the body to create the antibodiesSame as PfizerAdenovirus is used to carry the spike gene into the bodyAttenuated cold virus is used for the first dose and a different vector is used for the 2nd dose.
No. of doses222212
Dosage Schedule (Gap between the 1st and 2nd dose)8-12 weeks apart4 weeks apart21-28 days (3-4 weeks) apart. WHO recommends a delay of upto 42 days3-4 weeks apart3 weeks apart
Effectiveness against variants70% after 1st dose
90% after both doses
81%95% effectiveness. Pfizer claims it to be effective against the SouthAfrican variant.94.1% with both dosesCNBC reported an effectiveness of 64% against the southAfrican variant, around mid march92%
Special RemarksAccording to the non published data, effectiveness increases if the gap between the 1st and the 2nd dose is increased, within the range.Pfizer is the only vaccine, authorised for use in children <= 12 years. Remains stable for 3 months at refrigerator temperature. Claims a high efficacy against preventing hospitalisation and deaths in positive tested patients.

All the vaccines come with their mentioned side effects. It should be understood that there are certain symptoms that maybe experienced upon vaccination, however, it does not imply in any sense, not to get a jab.

There have been many concerns regarding the use of J&J vaccine, since its inception. Some women in the reproductive age group were reported to experience potentially dangerous blood clots (suggestive of cerebral venous sinus thrombosis), 6-13 days after vaccination. However, following standard research, the CDC and FDA found that the benefits of the vaccine outweighed the risks and it was cleared for public use, with “WARNING LABELS”.

Warning Labels For J&J Vaccine

The young are more prone to develop side effects due to their robust immune system.

Women are more susceptible to develop complications because oestrogen hormone in women, elevates the immune responses, whereas, the testosterone hormone in males, dampens them. Also, many immune modulating genes are found on the X chromosomes.

Who and When of vaccination?

There is a situation of utter confusion, especially in our country, regarding vaccination. It needs to be understood that to get the curve down, we need to be vaccinated in huge numbers.

As of May 19, 2021, there was a statement released by Sri Rajesh Bhushan, Union Health Secretary, regarding the uncanny attitude towards vaccines. It was declared that –

A jab can be taken 3 months after recovering from Covid 19 infection.

It was also made clear that all pregnant and lactating women were safe to get vaccinated.

Patients with any other serious, general illness requiring hospitalisation, should defer at least 4-8 weeks before getting vaccinated.

People can donate blood after 14 days of either getting vaccinated OR testing RT-PCR negative for COVID.

Experts recommend that the protection that one develops after getting infected by the virus, stays for atleast three months. Vaccine is administered when the already formed antibodies may have become redundant, and hence the gap of three months expained.

The Non Injectable Options

Apart from the obvious injectable vaccines, there have been much ongoing research for other alternative routes of administering the vaccine. Nasal and Oral alternatives are also being explored.

  • Bharat Biotech headed nasal vaccine is currently in the final phase of clinical trials.
  • Viral vector based nasal vaccine is also being developed at University of Hong Kong, China. It’s in the Phase II trial.
  • A protein subunit based nasal vaccine researched by Iran, is also in its second clinical phase.

Nasal Immunisation aims to replicate this natural immunisation process in a more effective manner.

Professor Micheal Russell, PhD, Department of Immunology & Microbiology, University of Buffalo, New York

Also, some of the oral options being developed are –

  • Maryland’s Vaxart – advancing to phase III trials
  • California’s ImmunityBio has a non replicating human adenovirus vector, it’s in the phase I trial.
  • Australia’s Symvivo/Merck’s DNA based vaccine is in phase I trial.

Mucosal antibodies generate Immunoglobulins A (Ig A), rather than Ig G, generated by the conventional intramuscular vaccines. These vaccines offer some advantages as well as they have their shortcomings.

AdvantagesDisadvantages
These vaccines remain stable at room temperature. They do not offer a long lasting immunity.
They are easy to administer.Mucosal surface contains barriers to pathogens, which interferes with the ability of vaccines to access and activate the mucosal immune system. This leads to poor immunogenicity and a faster waning immunity.

We may choose any of the options that have been approved for common usage, but it is prudent to understand the importance of vaccination. We can hope to eradicate the virus only if we all unite and get vaccinated.


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