COVID-19 vaccines offer better protection than natural immunity alone

Vaccination efforts are underway in many countries as the threat of coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues. Globally, over 4.47 billion vaccine doses have been administered, with many countries striving to immunize as many people as they can.

Now, the U.S. Centers for Disease Control and Prevention (CDC) reports that among people who were previously infected with SARS-CoV-2, those who were still unvaccinated are more likely to be reinfected than those fully vaccinated after prior infection.

The case-control study, which appeared in CDC’s Morbidity and Mortality Weekly Report (MMWR), showed that being unvaccinated was tied to 2.34 times the odds of reinfection compared with being fully vaccinated.

SARS-CoV-2 reinfection

Reinfection with human coronaviruses, including SARS-CoV-2, has been documented. At present, limited evidence concerning the protection provided by vaccination against reinfection is available.

Though evidence suggests that antibody responses after being vaccinated provide better neutralization of some circulating SARS-CoV-2 variants than natural infection, limited studies support the benefit of vaccination for previously infected individuals.

The report, which detailed the benefits of vaccination for previously infected persons, covered the link between vaccination and SARS-CoV-2 reinfection in Kentucky between May and June 2021, among those who had previous COVID-19 infection in 2020.

Overall, there were 246 case patients and 492 controls. The population included in the study had been infected with COVID-19 between October and December 2020. Of the 246 case patients, 20.3 percent were fully vaccinated, compared with 34.3 percent of controls.

Those with previous unvaccinated infections are 2.34 times more likely to be reinfected with SARS-CoV-2 than those who had their complete vaccine doses.

“This finding supports the CDC recommendation that all eligible persons be offered COVID-19 vaccination, regardless of previous SARS-CoV-2 infection status,” the researchers noted in the study.

Vaccine efficacy

COVID-19 vaccines are safe and effective in preventing serious COVID-19, particularly for vulnerable populations. These include the elderly and those with underlying medical conditions.

In a second publication from MMWR, the researchers showed that vaccines prevented COVID-19 related hospitalizations among the highest risk age groups. The report revealed that being fully vaccinated adults between the ages of 65 and 74 prevented hospitalization by 96 percent for Pfizer-BioNTech, 96 percent for Moderna, and 84 percent for Janssen COVID-19 vaccines. For those over 75 years old, the effectiveness of full vaccination for preventing hospitalization was 91 percent for Pfizer-BioNTech, 96 percent for Moderna, and 85 percent for Janssen COVID-19 vaccines.

The CDC added that COVID-19 vaccines prevent severe illness, hospitalization, and death. Further, vaccines make people more likely to experience milder or shorter illnesses than those who never had a vaccine shot.

Currently, the CDC recommends that residents 12 years and above get the vaccines against SARS-CoV-2.

“If you have had COVID-19 before, please still get vaccinated. This study shows you are twice as likely to get infected again if you are unvaccinated. Getting the vaccine is the best way to protect yourself and others around you, especially as the more contagious Delta variant spreads around the country,” CDC Director Dr. Rochelle Walensky said in a statement.

To date, the global number of cases continues to increase, topping 203 million. The pandemic has claimed over 4.31 million lives globally. The United States reports the highest number of cases, with over 36 million cases and over 618,000 deaths.

India and Brazil follow with over 31.9 million cases and 20.2 million cases, respectively.

Journal references:
  • Cavanaugh, A., Spicer, K., Thoroughman, D. et al. (2021). Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination — Kentucky, May–June 2021. U.S. Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR).
  • Moline, H., Whitaker, M., Deng, L., Rhodes, J. et al. (2021). Effectiveness of COVID-19 Vaccines in Preventing Hospitalization Among Adults Aged ≥65 Years — COVID-NET, 13 States, February–April 2021. . U.S. Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR).
Angela Betsaida B. Laguipo

Written by

Angela Betsaida B. Laguipo

Angela is a nurse by profession and a writer by heart. She graduated with honors (Cum Laude) for her Bachelor of Nursing degree at the University of Baguio, Philippines. She is currently completing her Master's Degree where she specialized in Maternal and Child Nursing and worked as a clinical instructor and educator in the School of Nursing at the University of Baguio.


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  1. Mac Borling Mac Borling United States says:

    So the CDC stops tracking "breakthrough" cases in May unless they result in hospitalization or death. Then a few months later they issue a completely misleading  press release, "New CDC Study: Vaccination Offers Higher Protection than Previous COVID-19 Infection".  The study that the CDC is linking doesn't even outline the severity of the reinfections including the hospitalizations and deaths that they apparently only care about for "breakthrough" cases?  

    They have all but eliminated any confidence in their recommendations over this pandemic.

  2. Danny Key Danny Key United States says:

    It is hard to say that the title of this article is correct, at least based on this CDC publication.
    This is a case Control Study with a few challenges. The background does not mention cohort studies already performed in this area (the cohort studies which already exist are a higher level of evidence than this type of case-control investigation), but instead incorrectly states "few real world epidemiologic studies exist to support the benefit of vaccination for previously infected individuals." They should have cited NEJM Dec 23 regarding those with COVID antibodies, and SIREN study in Lancet comparing natural immunity with vaccination, both of which address the potential protective effect of recovery from previous infection.  Does not provide number of total cases from which cases and controls were selected.  Reader should beware that odds ratios, often used in case-control studies, may exaggerate a difference between groups. The background infers that the authors intend to show "the benefit of vaccination for previously infected persons."  This article does not show the benefit of vaccination in previously infected individuals, since they did not include a comparison group of previously infected patients who were also vaccinated.  Note: what is really needed is more meaningful outcome studies, with endpoints that matter, such as hospitalization, endotracheal intubation and mortality.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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