Get Vaccinated Even If You’ve Gotten COVID-19, Study Suggests


A CDC investigation shows 2.3 times the number of reinfections with natural immunity compared to breakthrough infections in those who are vaccinated.

Even those who’ve had COVID-19 should be vaccinated, suggests data from the Centers for Disease Control and Prevention (CDC). A study in the CDC’s Morbidity and Mortality Weekly Report (MMWR), shows 2.3 times the number of reinfections with natural immunity compared to breakthrough infections in those who are vaccinated.

CDC investigators examined data from Kentucky residents infected with COVID-19 in 2020. They compared the vaccination status of those reinfected in May and June 2021 to residents who had not been reinfected.

“May and June were selected because of vaccine supply and eligibility requirement considerations; this period was more likely to reflect resident choice to be vaccinated, rather than eligibility to receive vaccine,” the study states. “Control participants were Kentucky residents with laboratory-confirmed SARS-CoV-2 infection in 2020 who were not reinfected through June 30, 2021.”

The possible damage caused by COVID-19 variants—such as the Delta variant and the lambda variant—seemed to loom large in the CDC investigators’ considerations. The new variants might weaken the protection provided by having been previously infected by SARS-CoV-2, the MMWR study states.

“For example, a recent laboratory study found that sera collected from previously infected persons before they were vaccinated provided a relatively weaker, and in some cases absent, neutralization response to the B.1.351 (Beta) variant when compared with the original Wuhan-Hu-1 strain,” the study states.

CDC investigators add that “the findings from this study suggest that among previously infected persons, full vaccination is associated with reduced likelihood of reinfection, and, conversely, being unvaccinated is associated with higher likelihood of being reinfected.”

But what about those who are partially vaccinated?

“The lack of a significant association with partial versus full vaccination should be interpreted with caution given the small numbers of partially vaccinated persons included in the analysis (6.9% of case-patients and 7.9% of controls), which limited statistical power,” the study states “The lower odds of reinfection among the partially vaccinated group compared with the unvaccinated group is suggestive of a protective effect and consistent with findings from previous studies indicating higher titers after the first mRNA vaccine dose in persons who were previously infected.”

Meanwhile, research unveiled by Public Health England (PHE) in its latest Variant Technical Briefing underscores how the variants pose such a challenge to health care systems. It shows that the Delta variant is still overwhelmingly dominant across the United Kingdom, accounting for approximately 99% of cases. The briefing includes updated hospitalization data for Delta, which shows that in the period since the last update on July 19, 2021: “1467 people were hospitalized with cases of Delta confirmed by sequencing or genotyping."

Of these, 808 (55.1%) were unvaccinated, while 512 (34.9%) had received both doses of a vaccine. While vaccines provide high levels of protection, they are not 100% effective and will not stop everyone from catching COVID-19. As more of the population gets vaccinated, we could see a higher relative percentage of vaccinated people in the hospital.

“Currently, 58% of the population in the United Kingdom are fully vaccinated,” according to the New York Times. “This would equate to an overall vaccination effectiveness in preventing hospitalizations of 35%.”

This supports the Health Ministry of Israel’s data which shows waning of vaccine protection in those who are over 60 years of age and are more than 5 months post vaccination. As Infection Control Today® reported, 8.6% of breakthrough infections in this group of elderly patients have resulted in hospitalization and 2% have resulted in death.

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