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COVID Vaccination and Breakthrough Delta Infection

Published on Aug 18, 2021 and last reviewed on Jan 21, 2022   -  4 min read


The recent challenge of the ongoing pandemic is about the breakthrough COVID infections, especially of the Delta and Delta Plus variant in fully vaccinated people, serving as the infection transmitters. Scroll down to find more facts regarding vaccines, Delta variants, and breakthrough infection.

COVID Vaccination and Breakthrough Delta Infection


Since the day COVID hit the planet in December 2019, it has been continuously mutating to develop into more virulent strains, with the recent severe ones being the Delta and Delta Plus variants. Simultaneously, vaccines’ advent created a significant impact in reducing COVID complications and death rates.

While the whole world was getting accustomed to COVID by implementing defensive disease control strategies, especially by developing vaccines and increasing the vaccination rates among the population, the Delta variants posed a challenge to humankind.

Breakthrough infections among the vaccinated population and such people spreading the COVID infection back to the unvaccinated population have led to an unbreakable incessant COVID chain.

Why Delta Variant of SARS-CoV-2 is Concerning:

The Delta variant (B.1.617.2) of SARS-CoV-2 (severe acute respiratory syndrome Coronavirus 2) is a variant of the original Coronavirus with its origin in India. This strain is more than twice as contagious as the original and previous strains, meaning it could infect more people fast with more infections than previous strains. It is also confirmed that Delta variants cause severe illness compared to their previous variants.

Due to its high contagiousness and infectivity, the Delta variant became the dominant variant causing fresh COVID infections in the United States, United Kingdom, India, and several parts of the world. It increases the risk of hospitalization in unvaccinated people.

I Am Fully Vaccinated, Will I Contract COVID?

Whether or not you are fully vaccinated, the chances of contracting COVID are high if you do not follow social distancing, hand sanitation, and wearing masks. This is because of the low vaccinated to unvaccinated ratio and the evolution of more virulent strains.

Eventually, the infection from unvaccinated people gets transmitted to the vaccinated ones and vice versa, thereby maintaining the COVID spreading chain intact.

Although vaccines offer life-saving protection against coronavirus infection, they are not 100% effective. This is true for any vaccine. Hence breakthrough infections were an expected scenario amidst the vaccinated population, especially with the evolution of the Delta and other suspected variants like the Omicron.

What Does Breakthrough Infection Mean?

When fully vaccinated, people contract COVID infection with or without symptoms; it is called breakthrough COVID infection. And the percentage of breakthrough infections is becoming high with the emergence of more virulent strains like the Delta.

All viruses in an epidemic or pandemic mutate constantly. But the fear is that if the rate of infection spread is not controlled, these mutations continuously lead to the development of newer strains with more contagiousness. The more the viruses spread within the population, the more virulent they become and resist vaccines’ protection.

A vaccinated person with breakthrough COVID infection may or may not develop symptoms.

If symptoms are present, they resemble the signs of usual COVID infection like runny or stuffy nose, body pain, fever, headache, loss of smell and taste, diarrhea, fatigue, shortness of breath, etc. The infection severity and duration of infection prevailing in the bodies of vaccinated people are less in comparison to unvaccinated people. Some people can also be asymptomatic.

Vaccinated People and COVID Transmission:

Recent studies from various parts of the world suggest that the viral load that vaccinated COVID infected people carry in their bodies is similar to that of unvaccinated people. Also, the death of a fully vaccinated 63-year-old woman from Mumbai, India, was reported, adding more concerns about vaccine efficacy and Delta strains.

Even if someone vaccinated is asymptomatic, testing their nasal swabs for COVID has revealed increased viral load due to the highly prevalent Delta strain within the community. It is believed that the inner nasal lining and throat continued to remain as the reservoirs of Coronaviruses in vaccinated individuals. With compromised COVID control protocols among the vaccinated people, these viruses spread to other unvaccinated people (also vaccinated) while talking, sneezing, coughing, and contact with respiratory droplet-contaminated hands.

More viral particles were found in the airways of Delta variant-infected vaccinated individuals. Viral loads were thousandfold increased in Delta infection comparatively, reports a Chinese study.

Do Vaccines Offer Protection Against Delta Infection?

All scientists, researchers, and physicians have constantly been stressing the importance of vaccines in the battle of COVID. No doubt, vaccines offer protection against COVID infection. The Delta variant does evade the vaccine-induced antibodies in our body. Still, vaccines reduce the severity of illness, reduce the need for hospitalization, and decrease death rates due to health complications. And that is why everyone is concerned with the vaccine rates. Even as of now, only a few populations have been vaccinated worldwide. Increasing vaccine manufacture with a rapid rise in the curve of vaccination rates is of high priority.

If we question the vaccine efficacy against the Delta variant and other newly emerging variants, then as per the studies available till now, we found the neutralization activity of sera of vaccinated people against Delta variant is detectable but less when compared to the neutralization activity of vaccinated sera against the original Wuhan strain.

Infection Transmission From the Vaccinated to the Unvaccinated:

A study found that people who received a single dose of the COVID vaccine developed little to no neutralizing antibodies against the Delta infection, while those who received both shots developed neutralizing activity that was three to five folds less potent against the Delta variant than the Alpha variant. These studies emphasize the protective measures that vaccinated individuals must follow and their risk of getting infected and transmitting the same to others.

Hence experts suggest physical distancing, masking, and hand sanitation be followed even in fully vaccinated individuals. Asymptomatic vaccinated individuals harbor Coronavirus inside their nose and throat that they might transmit to whoever they meet and talk to without a mask.

In several countries, more than 90% of the COVID cases at present are due to the Delta infection. With such a deadly strain prevailing within the communities and more new variants of concern of the coronavirus emerge, resulting in a surge in cases, getting vaccinated is the only powerful weapon in hand.


Regardless of your vaccination status, apex health bodies recommend masking, social distancing, and hand sanitation to be followed while outdoors. Meanwhile, studies, researches, and trials to develop nasal COVID vaccines and booster shots are in progress; disease control and prevention of infection transmission are the need of the hour to put a stop to the viral mutations. Until a decent percentage of people get vaccinated, and COVID control protocols are strictly followed, COVID infection circulates within the planet like a boomerang.

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Last reviewed at:
21 Jan 2022  -  4 min read




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