Omicron More Likely Than Delta to Cause COVID-19 Reinfection

Infection Control Today, Volume 26, Issue 1

Exactly how the new variant of COVID-19 fares against vaccinated people continues to be studied.

The COVID-19 variant Omicron is 3 times more likely to reinfect individuals than the Delta variant, according to a preprint study from South Africa,1 where the latest iteration of COVID-19 first surfaced on November 25, 2021. Meanwhile, how Omicron may affect individuals who have been vaccinated continues to be explored, although Pfizer/BioNTech announced on December 8, 2021, that its vaccine is very effective against Omicron.2 In addition, health experts around the world stand united in saying that vaccination remains the best defense against SARS-CoV-2.

“Population-level evidence suggests that the Omicron variant is associated with substantial ability to evade immunity from prior infection,” wrote investigators at Stellenbosch University in South Africa. “In contrast, there is no population-wide epidemiological evidence of immune escape associated with the Beta or Delta variants. This finding has important implications for public health planning, particularly in countries [such as] South Africa with high rates of immunity from prior infection.”

Investigators based their findings on an examination of approximately 2.8 million patients with positive COVID-19 samples, 35,670 of whom tested positive for COVID-19 and were considered reinfections.

Study coauthor Juliet Pulliam, PhD, said in a statement that “contrary to our expectations and experience with the previous variants, we are now experiencing an increase in the risk of reinfection that exceeds our prior experience.”2

Harry Moultrie, MD, senior medical epidemiologist at the Centre for Tuberculosis at the National Institute for Communicable Diseases (NICD) in South Africa, said in the statement that “our most urgent priority now is to quantify the extent of Omicron’s immune escape for both natural and vaccine-derived immunity, as well as its transmissibility relative to other variants and impact on disease severity.”2

Eugene Cloete, PhD, deputy vice-chancellor of research, innovation and postgraduate study at Stellenbosch University, said in a statement that “given the pandemic stage that we are in, it is our responsibility to make the broader public aware of any new variant. We have done this before and believe it is our scientific and ethical responsibility to continue to timeously share information about breakthrough variants as and when they are identified. Not making this important information public would be irresponsible science.”3

Initial data available from the NICD show the concern to be well-founded.

The study’s authors note that “urgent questions remain regarding whether Omicron is also able to evade vaccine-induced immunity and the potential implications of reduced immunity to infection on protection against severe disease and death.”

Data released on December 8, 2021, show that serum antibodies induced by the Pfizer/BioNTech COVID-19 vaccine neutralized the Omicron variant after 3 doses.4

  1. References:

    Pullman JRC, van Schalkwyk C, Govender N, et al. Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa. Published online December 2, 2021. Accessed December 3, 2021. https://www.medrxiv.org/content/10.1101/2021.11.11.21266068v2
    Parkinson J. Pfizer/BioNTech vaccine looks to be very effective against Omicron. Infection Control Today®. December 8, 2021. Accessed December 8, 2021. https://www.infectioncontroltoday.com/view/pfizer-biontech-vaccine-looks-to-be-very-effective-against-omicron
    Announcement of new B.1.1.529 variant (Omicron). November 29, 2021. Accessed December 7, 2021. http://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=8785
    Data from South Africa suggests greater risk of reinfection from Omicron. 2021. December 2, 2021. Accessed December 7, 2021. http://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=8800