Author
With the delta variant making up over 93% of COVID-19 cases in the U.S. at the end of July 2021, questions arise about how to stay protected against evolving forms of the SARS-CoV-2 virus. Here, pediatrician and infectious disease specialist Dr. Lilly Cheng Immergluck of Morehouse School of Medicine answers some common questions about variants and what you can do to best protect yourself.
1. What are variants and how do they emerge?
Viruses mutate over time to adapt to their environment and improve their survival. Over the course of the pandemic, SARS-CoV-2, the novel coronavirus that causes COVID-19, has mutated enough to change both its ability to spread through the population and its ability to infect people.
These new strains are called variants. The U.S. Centers for Disease Control and Prevention currently classifies variants into three categories, listed in order of least to most concerning:
Variant of Interest (VOI): Have features that may reduce your immune system’s ability to prevent infection. For example, you might have heard of VOI eta, iota or kappa.
Variant of Concern (VOC): Are less responsive to treatments or vaccines and more likely to evade diagnostic detection. They tend to be more transmissible, or contagious, and result in more severe infections. Alpha and delta are VOCs, for instance.
Variant of High Consequence (VOHC): Are significantly less responsive to existing diagnostic, prevention and treatment options. They also result in more severe infections and hospitalizations. There have not been any VOHCs identified so far.
The World Health Organization uses similar classifications, but their definitions may differ from the CDC’s U.S.-based ones, as variant features and effects may differ by geographic location.
2. Are variants always more harmful?
A variant may be more or less dangerous than other strains depending on the mutations in its genetic code. Mutations can affect attributes like how contagious a viral variant is, how it interacts with the immune system or the severity of the symptoms it triggers.
For example, the alpha variant is more transmissible than the original form of SARS-CoV-2. Studies show it’s somewhere between 43% to 90% more contagious than the virus that was most common at the start of the pandemic. Alpha also is more likely to cause severe disease, as indicated by increased rates of hospitalization and death after infection.
Even more extreme, the delta variant is reported to be nearly twice as contagious as previous strains and may cause even more severe disease among those who are unvaccinated. The viral load of those infected with delta – meaning the amount of virus detected from the nasal passages of an infected person – is also reported to be over 1,000 times higher than in those infected with the original form of SARS-CoV-2. Recent evidence also suggests that both unvaccinated and vaccinated people carry similar viral loads, further contributing to the especially contagious nature of this variant.
3. Which variants are most common in the US?
Over the course of a few months, the delta variant has become the predominant strain in the U.S., accounting for the vast majority of COVID-19 cases at the end of July 2021.
But there are regional variations across the country. As of July 31, the CDC estimated that the alpha variant represented over 3% of cases identified in a region of eight states that includes Georgia, Florida and Tennessee, compared with less than 1% in the region that includes Iowa, Kansas, Missouri and Nebraska. The CDC tracks variants in cooperation with state health departments and other public health agencies. COVID-19 infection samples from across the country are genetically sequenced each week to identify existing and new variants.
And new variants will likely continue to appear as the virus evolves. Delta plus, for instance, is a sub-lineage of delta. The effects of this subvariant are yet to be determined.
4. How are vaccines holding up against variants?
Researchers are working to figure out how effective the three COVID-19 vaccines currently authorized for emergency use in the U.S. are at preventing infection from variants in “real-world” conditions where variant distribution and frequency constantly change. Several preliminary studies that have not yet been peer-reviewed suggest that these vaccines are still effective in preventing COVID-19-related serious infections and death.
No vaccine is perfect, however, and breakthrough COVID-19 infections are possible in those who are vaccinated. Older adults and those with immunocompromising conditions may be at increased risk to have these breakthrough infections.
Thankfully, fully vaccinated individuals generally experience milder COVID-19 infections. For example, a study analyzing COVID-19 cases in England estimated that two doses of the Pfizer BioNTech vaccine are 93.7% effective in preventing symptomatic disease from the alpha variant and 88% effective from delta. A different study in Ontario, Canada, that is not yet peer-reviewed reported that the Moderna vaccine is 92% effective in preventing symptomatic disease from alpha.
5. How can I stay safe?
How cautious you should be depends on a number of individual and external factors.
One factor is whether you’re fully vaccinated. Nearly all - 99.5% - of COVID-19 deaths in the U.S. over the past few months were among unvaccinated people.
The most recent CDC guidelines recommend that everyone wear a mask in areas of substantial or high transmission, regardless of whether or not they’re vaccinated. More caution should especially be taken if you aren’t fully vaccinated or have a weakened immune system.
[Understand new developments in science, health and technology, each week. Subscribe to The Conversation’s science newsletter.]
Another factor to consider is the level of community transmission and the proportion of unvaccinated people in your local community. For example, someone who lives in an area that is below the national average for COVID-19 vaccinations may have a higher chance of encountering someone who is unvaccinated – and so more likely to spread the coronavirus – than someone in an area with higher vaccination rates.
Finally, there are still a significant number of people who are at high risk of COVID-19, including children. As of Aug. 3, 2021, only 29.1% of children ages 12 to 15, and 40.4% of those ages 16 and 17, had been fully vaccinated. The American Academy of Pediatrics and the Children’s Hospital Association note that 4,292,120 total child COVID-19 cases had been reported as of Aug. 5. Children make up 14.3% of reported COVID-19 cases. If your child is unvaccinated, the best way you can protect them and other unvaccinated members of your household is to get yourself vaccinated and have everyone wear a mask in indoor public spaces.
Guidelines provided by public health agencies are simply that – general guidelines. They are not tailored to be prescriptive for each individual and their personal risk assessments.
Vaccines remain the best protection against every strain of the novel coronavirus. But masking, social distancing and avoiding crowds and poorly ventilated indoor spaces add extra layers of protection against breakthrough infections and lower your risk of inadvertently spreading the virus.
Before you go…
Evidence-based news and analysis has never been more important. But we need support from readers like you to keep going. If you believe in the importance of independent, fact-based journalism please become a monthly donor today.
Misha Ketchell
Editor
(Sources: The Conversation)
Đăng nhận xét