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Is a Booster Dose Necessary For Delta and Other Variants?

Published on Aug 11, 2021 and last reviewed on May 13, 2022   -  5 min read


With an increasing number of delta and omicron recombinant cases, it is essential to know about the delta and omicron coronavirus and the effectiveness of COVID-19 vaccines against these forms. Also, there have been speculations about having a booster dose of the vaccine.

Is a Booster Dose Necessary For Delta and Other Variants?

Delta Variant of SARS-CoV-2

The delta variant of the coronavirus was first recorded in India in January 2021. The delta variant is a problem of concern for two main reasons: the increased rate of transmissibility and the degree of severe illness caused by it. Of the daily cases in the United States, about 82 percent were caused by delta variants, and in the United Kingdom, delta variants accounted for about 99 percent of cases. The Chinese Academy of Medical Sciences has stated in a study that the viral load in the delta variant is 1000 times higher than that of previous variants of SARS-CoV-2.

Effectiveness of Vaccines Against Delta Variant

Although no vaccine is 100 percent effective in preventing an infection, the rate of mortality and hospitalization is relatively reduced in people who have been fully vaccinated. Like other forms of COVID-19, the delta variant also has the same effect in terms of vaccination. Ascertaining the efficiency of COVID-19 vaccines against the delta variants has been difficult due to the limited availability of research data. Although only a few studies have been done to determine the efficacy of COVID-19 vaccines on delta variants.

Let us discuss the effect of WHO-approved vaccines on the delta variants.

Pfizer Vaccine:

A study by public health England has reported that getting two doses of the Pfizer-BioNTech vaccine prevents delta variant infection by around 80 percent. In symptomatic cases, the efficiency is 88 percent, and in patients who need hospitalization, it is the highest at 96 percent.

A report by the journal Nature states that a single dose of Pfizer vaccine hardly protects against the delta variant. On average, the efficacy level of the Pfizer vaccine ranges between 64 to 96 percent against the delta variants in fully vaccinated people.

Moderna Vaccine:

Few studies have reported that the level of antibodies produced by the Moderna vaccine in the case of delta variant is higher than that produced in response to beta forms. On the other hand, it is lower when compared with the alpha variants of the virus.

Reports by the Canadian study indicate that the Moderna vaccine is 72 percent effective against the delta variant. Even a single dose of Moderna vaccine provides good protection against the delta forms, and the protection is higher when the two doses of vaccine are taken. A few of the researchers of New York have reported that the Moderna is equally effective as Pfizer, with an efficiency of about 94 to 95 percent when it comes to delta variants.

Johnson and Johnson Vaccine:

Clinical trials have proved the Johnson and Johnson vaccine to be 71 % effective against hospitalization due to delta variant infection and 96 % effective against death from delta variant infection.

AstraZeneca Vaccine:

The AstraZeneca vaccine administered in India in the name 'Covishield' has been proven to be the most influential vaccine against the delta variant, with an efficiency rate of 92 percent. No death cases among delta variants are reported in the people who have been fully vaccinated with the AstraZeneca vaccine.

Omicron Variant of SARS-CoV-2

Another variant of coronavirus that has emerged in South Africa was designated as a variant of concern by the WHO on November 26, 2021. Omicron was believed to be highly transmissible (no sources) but less severe and the number of COVID-19 cases started rising around the month of January. This variant exhibited the usual symptoms like fever, cough, fatigue, and loss of smell and taste. This wave was a combination of delta and omicron variants. It raised a lot of speculation regarding the vaccine’s efficiency against these two variants.

Effectiveness of Vaccines Against Omicron Variant

Vaccines are found to have great efficiency against Omicron infection. Studies suggest a booster dose along with the initial two shots, provides efficiency of 86 %. Therefore, the vaccines will have an effect on the increased transmissibility suspected with the Omicron variant.

The COVID-19 pandemic is still hanging around the corner, raising the speculation about the need for a booster dose. Let us briefly discuss what a booster dose is and why it is administered, and in specific, the current need for a COVID booster dose.

What Is a Booster Dose?

A booster dose, in general, refers to re-exposure to immunizing antigen by the administration of an extra vaccine in addition to the primary dose.

Why Is a Booster Dose Needed?

Depending on the number of specific antibodies, the need for a booster dose is evaluated. It is determined with the help of an anamnestic response, which assesses the antibodies produced following an antigen stimulus. If the number of specific antibodies is less, it cannot protect against the particular disease; thereby, the purpose of vaccination is not met.

Need for the COVID-19 Booster Dose:

Research carried out by the Israeli health ministry has stated that the protection against COVID-19 in people who had their vaccination in April 2021 is around 75 percent whereas, it is only 16 percent in people who got their vaccine in January 2021. It has posed the need for a booster. And, therefore on September 22, 2021, the FDA has approved the use of a booster dose of Pfizer-BioNTech in individuals above the age of 18 years. And on October 20, 2021, the booster shot of the Moderna and Johnson & Johnson vaccine was approved. As of November 29, 2021, the Centers for Disease Control and Prevention (CDC) of the United States has further strengthened its recommendation to get the vaccine with the emerging Omicron variant of SARS-CoV-2.

The following table depicts when and who should take the booster shot of the COVID vaccines:

delta varient

Effect of Booster Dose Against the Delta Variants:

Recent trials have reported that the booster dose of the Pfizer vaccine has the ability to produce five times more antibodies in people between the age group of 18 to 55 years and eleven times more antibodies in people between 65 to 85 years. Pfizer-BioNTech, Moderna, and Johnson & Johnson has received approval from the CDC of the United States to administer the third dose to protect against the omicron, delta, and other new variants of the SARS-CoV-2 virus.

People have already started taking booster doses all over the world. The eligible candidates are advised to get the shots, to combat the increasing number of COVID-19 cases.

How to Protect Yourself From the Highly Contagious and Powerful Delta and Omicron Variant SARS-CoV-2 Virus?

As the cases of delta and Omicron variant COVID-19 are increasing in most parts of the world, it is high time we take adequate precautionary measures to protect ourselves and our loved ones from viral infection.

As like every other variant of COVID-19, the preventive measures to protect against COVID-19 infection are solely dependent on the following tetrad of factors:

Variant SARS-CoV-2 Virus

Vaccination is of prime importance at this time. However, it does not provide complete protection against the spread of infection, and it plays a vital role in reducing the chances of hospitalization and preventing deaths. Also, fully vaccinated people are comparatively less infectious than unvaccinated people, and the period of virus inhabitation in them is very low, leading to a decreased spread of infection. It eventually reduces the chain of spread and may serve as an effective tool to stop the persisting pandemic.

In addition to getting the vaccination at your turn, wearing masks while going out, maintaining a social distance of one meter or more, washing your hands frequently, and avoiding touching your nose, eyes, and mouth will help protect you from infection.


Last reviewed at:
13 May 2022  -  5 min read




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