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COVID-19 virus test results may vary based on time of day: Study

The research, published in the Journal of Biological Rhythms on Tuesday, found that people were up to two times as likely to have an accurate positive test result if they tested in the middle of the day compared to at night.

October 27, 2021 / 08:05 PM IST

The test sensitivity of SARS-CoV-2, the virus that causes COVID-19, may vary based on the time of the day and the our body’s biological clock, according to a study.

The research, published in the Journal of Biological Rhythms on Tuesday, found that people were up to two times as likely to have an accurate positive test result if they tested in the middle of the day compared to at night.

The finding supports the hypothesis that COVID-19 acts differently in the body based on our natural circadian rhythm, which has also been implied by studies of other viral and bacterial infections, the researchers said.

Circadian rhythm is our body’s natural, internal process that regulates the sleepwake cycle and repeats roughly every 24 hours. COVID-19 virus shedding — when infected cells release virus particles into the blood and mucus — appears to be more active in the middle of the day due to modulation of the immune system by our biological clock, the researchers said.

"Taking a COVID-19 test at the optimal time of day improves test sensitivity and will help us to be accurate in diagnosing people who may be infected but asymptomatic,” said Carl Johnson, a professor at Vanderbilt University in the US.


COVID-19 Vaccine

Frequently Asked Questions

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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The results indicate that viral load is lower after 8 p.m, according to the researchers.

If people choose to get tested at that time, there could be a higher chance of a false-negative result, they said.

A difference in COVID-19 viral shedding throughout the day is important information that may inform how we test for and treat the virus, the researchers said.

The peak shedding in the afternoon, when patients are more likely to interact with others or seek medical care, could play a role in increasing the spread of the virus in hospitals and the wider community, they said.

The researchers noted that further research is needed to confirm the diurnal — meaning active during the day — nature of SARS-CoV-2.

Experimentally testing patients who are infected with COVID-19 to see if individuals shed the virus differently throughout the day would have important public health implications, Johnson said.

The research can be used to optimise COVID-19 testing and improve test accuracy, he added.

The researchers believe temporal considerations may be leveraged to maximise the effectiveness of intervention strategies and even vaccine strategies.

Follow our full coverage of the coronavirus pandemic here.
first published: Oct 27, 2021 08:05 pm

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