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Breakthrough infections, viral load: What does this mean to you?

Abstract technical map showing COVID hotspots around the world Photo: Getty Images

With COVID-19, your best protection is vaccination. But what's this we're hearing about breakthrough infection? Viral load? It’s getting so complicated.

Here, VCU Health infectious disease expert Dr. Michelle Doll explains what breakthrough infection and viral load mean and why these terms are in the news.  

Dr. Michelle DollWhat is breakthrough infection? What is viral load?

Breakthrough infection refers to cases in which a person vaccinated against COVID-19 nonetheless becomes infected with the virus. Viral load refers to the amount of virus that can be detected in an infected person. High viral loads are concerning because they can mean the person is more infectious.

Why are breakthrough infection and viral load in the news these days?

The Centers for Disease Control and Prevention(CDC) recently published an analysis of clusters of infections driven by the delta variant of the SARS-CoV-2 virus. They found that a large portion of those infected in these clusters had been fully vaccinated. Furthermore, the viral loads were similar between those vaccinated and unvaccinated, suggesting that vaccinated individuals who develop breakthrough infections are very capable of transmitting the infection to others.

How likely am I to get a breakthrough infection? How contagious is the delta variant?

The delta variant is more contagious than other variants we have seen so far. According to the CDC, it is approximately 50% more infectious even than the alpha variant, originally seen in the United Kingdom (which in turn was approximately 50% more infectious than the original virus).

Risk of breakthrough infection depends on a lot of factors, including how prevalent COVID-19 is in the local community, how prevalent the delta variant is in a community, and to what extent risk mediation strategies are being employed, such as social distancing, masking, and avoiding high risk activities like large crowds and poorly ventilated indoor spaces.

Do people with breakthrough infection get just as sick as those who were never vaccinated?  

No, the good news is that the vaccine continues to offer protection from severe disease. In general, those who are vaccinated but go on to develop breakthrough infections are less likely to be hospitalized or develop severe disease. Of course, other factors can affect severity of disease, such as underlying medical conditions and the ability of the immune system to respond to the vaccine.

If most people with breakthrough infection don’t get severely ill, what’s the big deal?

If breakthrough infection can readily transmit the virus through our communities, it is a big problem that will put the brakes on efforts to resume the activities of our lives before COVID-19. If the pool of vulnerable people is large enough, then we can easily return to surges of infection that overwhelm the health care system.

We are not just talking about unvaccinated persons as vulnerable, though they certainly are, but even those who are fully vaccinated may have underlying medical conditions, extremes of age or poor immunologic response to the vaccine, placing them at risk if challenged with the infection.

Although many people recover from COVID-19 or have mild or no symptoms, there is no cure -- our in-hospital care remains supportive. More than 600,000 people in this country have died from COVID-19. It remains a deadly disease. We must do everything we can to avoid its spread.  

Does this mean the relaxation we’ve been enjoying in terms of mask wearing and social distancing must come to an end? Should I cancel my vacation plans?

The CDC is now recommending universal masking when indoors regardless of vaccination status. Many of the social distancing strategies may return in the near future. Travel plans may need to be re-evaluated. It really depends on the itinerary and what potential travelers are comfortable with. Make sure if you are traveling that you watch out for changes in travel requirements. Fully vaccinated persons have enjoyed travel privileges without mandatory COVID-19 testing pre- and post-trip within the United States for example, but this and other guidance could change in the future.

What about going back to the office or school? Concerts, athletics, movies and other social events?

Follow CDC guidance to do these activities as safely as possible. Wear a mask if indoors or even if outdoors in a large group of people. Wash your hands frequently. Check with venues regarding their plans for social distancing or cleaning procedures as applicable.  If symptoms of possible COVID-19 develop, even if mild, self-quarantine and seek testing.

I realize that we are all so tired of dealing with COVID-19, so returning to universal masking and social distancing is not at all what we want to hear! But if we can keep the case rates under control despite the delta variant, we are much more likely to be able to maintain these activities that are so important to our wellbeing.

For more information

For a variety of news and information on COVID-19 and how VCU Health is keeping patients safe, please visit our COVID-19 News Center

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