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Vaccines induce, not reduce immunity vs coronavirus

COVID-19 vaccines do not “decrease” the body's “immunity” at any point after vaccination and make people who have been inoculated susceptible to SARS-CoV-2 infection, contrary to a claim circulating on private chat groups.

The vaccines instead train the immune system to recognize the virus and create antibodies to fight off the disease without getting the disease itself.

A 218-word post FactRakers first tracked April 23 on Viber groups erroneously claims that vaccinated persons are very likely to get infected during the six weeks after being given their first dose because of the “low immunity” they will experience during that period.

The post reads in part:

When antibodies are forming in our body, our immunity decreases a lot.
When we take the second dose of the vaccine after the 21/28 days, our immunity decreases even more.
14 days after the second dose, when the antibodies are completely formed in our body, our immunity starts to grow rapidly.
During this one and a half month, due to low immunity, the chances of the corona virus entering our body are very high. It is due to an exposure to the virus at this vulnerable time that a person gets infected.

Clinical studies and real-world data have found that COVID-19 vaccination has prevented most people from getting COVID-19.

Studies on vaccines from Pfizer and Moderna, which come in two doses, also show people given the first dose already developing some protection against COVID-19, although “relatively weak,” making it necessary for people to get both doses to be adequately protected.

The U.S. Centers for Disease Control and Prevention said while fully vaccinated people are less likely to get sick, a small percentage will still get COVID-19 if they are exposed to the virus and called these “vaccine breakthrough cases.”

A person could still be infected with the coronavirus just before or just after vaccination and get sick because the vaccine did not have enough time to provide protection, according to CDC and the World Health Organization, not because it decreased immunity against the virus.

It typically takes a few weeks after vaccination for the body to produce T-lymphocytes and B-lymphocytes that will remember how to fight the virus, the CDC said.

WHO explains how vaccines that require two doses work:

(T)he first dose presents antigens, – proteins that stimulate the production of antibodies – to the immune system for the first time. Scientists call this priming the immune response. The second dose acts as a booster, ensuring the immune system develops a memory response to fight off the virus if it encounters it again.

Vaccine side effects such as a low-grade fever or pain or redness at the injection site are common and should not be equated with decreased immunity.

The process of building immunity can cause symptoms such as fever, the CDC said. “These symptoms are normal and are signs that the body is building immunity,” it said.

WHO has this explanation for the side effects a person might experience:

It’s common to experience some mild-to-moderate side effects when receiving vaccinations. This is because your immune system is instructing your body to react in certain ways: it increases blood flow so more immune cells can circulate, and it raises your body temperature in order to kill the virus. they are signs that the body’s immune system is responding to the vaccine, specifically the antigen (a substance that triggers an immune response), and is gearing up to fight the virus.

The inaccurate post being shared in the chat apps refers to a “21/28” interval between doses. Interval of doses varies per vaccine, however.

Sinovac, which is being administered in the Philippines, is taken four weeks or 28 days apart and AstraZeneca four to 12 weeks apart, according to the Department of Health.

The recommended interval between doses is 21 days for Pfizer-BioNTech’s vaccine and 28 for Moderna’s. However, however, up to 42 days between doses is permissible when a delay is unavoidable, the CDC said.

The interval between the two doses of Russia's Sputnik V can be extended from 21 days to three months, its news agency TASS said.

Johnson & Johnson’s vaccine is single-dose.

The inaccurate post also claims that immunity in the body “rises by 100 to 200 times” one-and-a-half months after vaccination “after which you are safe.” The 100- to 200-fold increase is unsupported by studies.

What one study did find is that previously infected people who got vaccinated generated high levels of antibodies within just a few days of getting the vaccine than those who had not been infected. Their immune responses were 10 to 20 times that observed in uninfected people, it said.


Centers for Disease Control and Prevention. (2021). COVID-19 vaccine second-dose completion and interval between first and second doses among vaccinated persons — United States, December 14, 2020−February 14, 2021.

Centers for Disease Control and Prevention. (2021). Janssen COVID-19 vaccine (Johnson & Johnson) questions.

Centers for Disease Control and Prevention. (2021, March 9). Understanding How COVID-19 vaccines work.

Centers for Disease Control and Prevention. (2021, April 15). Myths and facts about COVID-19 vaccines.

Centers for Disease Control and Prevention. (2021, April 21). What you should know about the possibility of COVID-19 illness after vaccination.

Collins, F. (2021, February 23). Is one vaccine dose enough after COVID-19 infection?

Department of Health (2021, March 18). What is the interval between the 1st and 2nd dose of Covid vaccine?

Krammer, F., Sirvastava, K., & Simon, V. (2021). Robust spike antibody responses and increased reactogenicity in seropositive individuals after a single dose of SARS-CoV-2 mRNA vaccine. medRxiv.

Livingston, E. (2021). Necessity of 2 doses of the Pfizer and Moderna COVID19 vaccines. JAMA, 325(9), 898. https://doi:10.1001/jama.2021.1375

TASS. (2021, April 26). Interval between Sputnik V doses can be extended up to three months, scientist says.

World Health Organization. (2021, March 31). Getting the COVID-19 vaccine.

World Health Organization. (2021, March 31). Side effects of COVID-19 vaccines.


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