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Risk Management

COVID-19 Roundup: Hybrid Immunity, Vaccination and Viral Loads, and Predicting Disease Severity

Vaccination and Hybrid Immunity1

Individuals who have been infected with SARS-CoV-2 and later receive the first dose of an mRNA COVID-19 vaccine may develop significant immunity against the disease, according to the results of several recent studies.

These individuals show immunity against a range of variants of COVID-19, as well as potential protection to other related coronaviruses. Individuals who have not been previously infected with SARS-CoV-2 may develop similar hybrid immunity through a booster dose of the vaccine.

“Based on all these findings, it looks like the immune system is eventually going to have the edge over this virus,” said Paul Bieniasz, PhD, who is the lead author of several of the studies.2 “And if we’re lucky, SARS-CoV-2 will eventually fall into that category of viruses that gives us only a mild cold.”

Viral Load and Vaccination Status3                    

Vaccinated and unvaccinated individuals who have tested positive for COVID-19 have no significant differences in viral load of SARS-CoV-2, according to the results of a recent study. There were no significant differences in viral load among infected individuals who were symptomatic vs asymptomatic.

Included in the study were 869 samples from individuals who tested positive for the Delta variant from the University of California, Davis’ Healthy Yolo Together and Unidos en Salud testing sites in San Francisco, California. The results indicated that while there were variations in viral load between the vaccinated and unvaccinated groups, there was no significant variations between both groups. 

“Our study does not provide information on infectiousness,” study author and director of the UC Davis Genome Center Richard Michelmore, PhD, said in a press release.4 “Transmission will be influenced by several factors, not just vaccination status and viral load.”

Saliva To Predict COVID-19 Severity5

Proteins found in saliva may be used to predict the severity of COVID-19 infection, according to the preliminary results of a recent study.

In this ongoing study, the researchers examined the relationship between the level of the protein cytokine and later infection in children at-risk for severe disease. A total of 400 children and adolescents aged 18 years or younger who tested positive for COVID-19 and presented to the emergency departments of the Children’s Hospital of Michigan and UPMC Children’s Hospital of Pittsburgh were included. Of the 400 total samples, 150 samples were included in the preliminary results.

When compared with children without severe infection, those with severe infection had higher levels of 2 cytokines. Further, microRNA levels were altered and significantly lower in individuals with severe infection.

 

—Leigh Precopio

 

References:

  1. Tan CW, Chia WN, Young BE, et al. Sarbecovirus neutralizing antibodies in BNT162b2-immunized SARS-CoV-1 survivors. N Engl J Med. 2021;385:1401-1406. http://dx.doi.org/10.1056/NEJMoa2108453 
  2. Doucleff M. New studies find evidence of ‘superhuman’ immunity to COVID-19 in some individuals. NPR. September 7, 2021. Accessed October 8, 2021. https://www.npr.org/sections/goatsandsoda/2021/09/07/1033677208/new-studies-find-evidence-of-superhuman-immunity-to-covid-19-in-some-individuals  
  3. Acharya CB, Schrom J, Mitchell AM, et al. No significant different in viral load between vaccinated and unvaccinated, asymptomatic and symptomatic groups when infected with SARS-CoV-2 Delta variant. MedRxiv.[Preprint.] Published online October 5, 2021. https://doi.org/10.1101/2021.09.28.21264262
  4. Fell A. Viral loads similar between vaccinated and unvaccinated people. News release. UC Davis; October 4, 2021. Accessed October 8, 2021. https://www.ucdavis.edu/health/covid-19/news/viral-loads-similar-between-vaccinated-and-unvaccinated-people
  5. Study uses saliva to predict COVID-19 severity risk in children. News release. Penn State College of Medicine; October 8, 2021. Accessed October 8, 2021. https://pennstatehealthnews.org/2021/10/saliva-predict-covid19-severity-kids/