It's too early to know what we can expect from the omicron variant of COVID-19, which was detected in South Africa and Europe in November and announced on Dec. 1 to have arrived in the United States. The World Health Organization says it presents a “very high" risk, based on mutations it shares with other viruses of concern and their impact, and it could lead to new surges worldwide. Abby Rudolph, associate professor of epidemiology and biostatistics at Temple's College of Public Health, studies disease transmission patterns and has followed COVID-19 and its variants. We asked Rudolph to help put omicron in perspective
Why are scientists more concerned about omicron than other COVID-19 variants? Is it more severe? More transmissible?
Rudolph: To date there have been several COVID-19 variants that have been deemed to be variants of concern (VOC):
- Alpha: first documented in the United Kingdom (VOC declared Dec 2020)
- Beta: first documented in South Africa (VOC declared Dec 2020)
- Gamma: first documented in Brazil (VOC declared Jan 2021)
- Delta: first documented in India (VOC declared May 2021)
Omicron is the most recently identified VOC and is of particular concern to scientists because of the large number of mutations, particularly those affecting the spike protein. The spike protein is important because (1) it is the protein that allows SARS-CoV-2 to bind to and infect human cells and (2) most vaccines target the spike protein and generate antibodies to attack it. As a result, these mutations may make the omicron variant more transmissible and the vaccine less effective. They may also make monoclonal antibody treatment less effective. It shares mutations with other previously identified VOCs (and new mutations not seen in other VOCs) that are thought to be associated with increased transmissibility and replication, a better ability to bind to the ACE2 receptor and infect human cells, resistance to neutralizing antibodies, and increased infectivity. There is some evidence that people are more likely to be reinfected with this variant than with other variants. More studies and data are needed to quantify the impact of this specific constellation of mutations on transmissibility, infectiousness and disease severity and to determine the extent to which the existing vaccines are effective against this variant.
Is it still too soon to know how much our current vaccines will protect against the omicron variant?
Rudolph: Yes. There are also different vaccines used across the globe, and some will likely perform better than others. For example, earlier studies showed that the AstraZeneca vaccine did not work as well against the beta and gamma variants.
How inevitable are virus variants and mutations that might elude the vaccines we have? Can anything be done to minimize or prevent them?
Rudolph: The best thing that can be done to prevent VOCs is to limit the number of new cases. Every time a person is infected, the virus makes copies of itself. When it makes copies of itself, it makes mistakes. You can think of this as similar to the mistakes you may make while typing on a keyboard very quickly. In some cases, the mistakes may be minor—e.g., spelling ‘the’ as ‘teh’, which will not meaningfully impact how the virus behaves. In other instances, the typos may completely change the meaning of what you were trying to type. In the case of virus mutations, these can increase or decrease its evolutionary fitness. If the mutations decrease the fitness of the virus, it will quickly die out and will never make headlines. When mutations improve viral fitness, this particular variant will out-compete the others for dominance. Mutations are inevitable, but they are the result of errors made by chance. The best thing we can do is limit opportunities for the virus to mutate. At the individual level, this means: (1) get vaccinated or get your booster shot, if eligible, (2) avoid crowded places and maintain physical distance, (3) wear a mask when in crowds or when you are with others who may not be vaccinated, (4) maintain good hand hygiene, and (5) ensure that indoor activities occur in places with good ventilation.
It is also extremely important that we focus on ensuring vaccine equity and reducing vaccine hesitancy. Vaccine hoarding by wealthy countries initially created vaccine inequities. Unequal access to vaccines combined with vaccine skepticism contribute to ongoing transmission in areas where fewer people are vaccinated and, consequently, to new opportunities for mutations to arise that deem a variant to be of concern. For example, in South Africa only 24 percent of the eligible population is vaccinated. It is important to remember that this is a global pandemic. As we have seen in the past, when a VOC is detected in one country it quickly spreads across the globe. To prevent future VOCs, it is crucial that we focus on interventions that increase access to vaccines and increase people’s willingness to be vaccinated.
What if current vaccines are ineffective? Should people still get their COVID-19 boosters, or wait for updated vaccines?
Rudolph: It is unlikely that vaccines we have will be completely ineffective, but they may not be as effective. Antibodies are proteins secreted by B cells, and these proteins typically target the spike protein—the protein that we know has a large number of mutations in the omicron variant. To date, most studies have focused on antibody response to the vaccines. However, T cells also help fight infections. A study by researchers at the University of Pennsylvania showed that the T cell response peaks after the second mRNA dose among those not previously infected with COVID-19 and after the first mRNA dose in those with prior COVID-19 infection. This suggests that even if the antibody response is weakened, the vaccines may still trigger an immune response that can make infection less severe or deadly.
Will wider access to rapid testing help? Is there anything else we can do as individuals?
Rudolph: If people had easy (and low/no-cost) access to rapid testing and could take a rapid test before every activity or interaction that might pose a risk of transmission—and then avoid those activities or interactions if the test is positive—we could prevent a lot of infections. The recommendations for individuals are virtually unchanged.