What is a breakthrough infection?

If you were completely vaccinated with COVID-19, you might have thought that you no longer had to worry about getting infected with the coronavirus. However, in addition to the increasing number of new COVID-19 cases worldwide and growing concerns about highly infectious strains such as delta variants, fully vaccinated people are tested for COVID-19. There are reports that it is positive in.

Members of the New York Yankees, Karaika, an Olympic gymnast in the United States, and Sajid Javid, the Minister of Health in the United Kingdom, are some of the people diagnosed with so-called “breakthrough infections.”

It may sound scary, but the bottom line is that existing COVID-19 vaccines are still very good at preventing symptomatic infections, and breakthrough infections rarely occur. But how common and how dangerous are they? Here is a guide to what you need to know.

What is a “breakthrough infection”?

No vaccine is 100% effective. Dr. Jonas Salk’s polio vaccine was 80% to 90% effective in preventing paralytic disease. Even with the gold standard measles vaccine, the efficacy of highly vaccinated populations during large outbreaks was 94%.

Similarly, clinical trials have shown that Pfizer and Modana mRNA vaccines are 94% to 95% effective in preventing symptomatic COVID-19. This is far more protective than originally expected.

A quick note: 95% vaccine efficacy does not mean that Shot protects 95% of people and the remaining 5% are infected with the virus.

Vaccine efficacy is a measure of relative risk. Under the same exposure conditions, a group of vaccinated people should be compared to a group of unvaccinated people. Therefore, consider a three-month study period in which 100 out of 10,000 unvaccinated people were infected with COVID-19. It is expected that five vaccinated people will get sick at the same time. This is 5% of 100 unvaccinated sick people, not 5% of the entire 10,000-person group.

When people become infected after vaccination, scientists call these cases “breakthrough” infections because the virus breaks through the defense barriers that the vaccine provides.

How common is a fully vaccinated COVID-19 infection?

Breakthrough infections are a bit more frequent than previously expected and are probably increasing due to the increasing predominance of delta variants. However, infections in vaccinated people are still very rare and usually cause mild or no symptoms.

For example, 46 states and territories in the United States voluntarily reported 10,262 breakthrough infections to the Centers for Disease Control and Prevention between January 1 and April 30, 2021. By comparison, there were a total of 11.8 million COVID-19 diagnoses during the same period.

Since May 1, 2021, the CDC has ceased monitoring breakthrough cases of vaccines unless hospitalized or died. By July 19, 2021, of the more than 159 million people who were fully vaccinated nationwide, 5,914 had a breakthrough infection with the COVID-19 vaccine that was hospitalized or died in the United States.

In one study from December 15, 2020 to March 31, 2021, 258,716 veterans who received two doses of the Pfizer or modelna vaccine counted 410 breakthrough infections. This is 0.16% of the total.

Similarly, a study in New York found that between February 1 and April 30, 2021, 86 COVID-19 breakthrough infections were found among 126,367 people who were fully vaccinated primarily with the mRNA vaccine. It was accepted. It accounts for 1.2% of all cases of COVID-19 and 0.07% of the fully vaccinated population.

How serious is the COVID-19 breakthrough infection?

The CDC defines a breakthrough vaccine as an infection in which the nasal swab can detect SARS-CoV-2 RNA or protein more than 14 days after completing all recommended doses of the FDA-approved COVID-19 vaccine. ..

Keep in mind that breakthrough infections do not necessarily mean that the person feels sick-in fact, 27% of the breakthrough cases reported to the CDC were asymptomatic. Only 10% of groundbreaking infected individuals are known to be hospitalized (some for reasons other than COVID-19) and 2% have died. For comparison, more than 6% of confirmed infections were fatal during the spring of 2020, when the vaccine was not yet available.

None of the breakthrough infections led to hospitalization in a study at a US military treatment facility. In another study, people who received a single dose of Pfizer vaccine and tested positive for COVID-19 were more likely to be vaccinated than those who were not vaccinated and tested positive. Virus is reduced by a quarter.

What increases the likelihood of breakthrough infections?

Nationally, an average of over 5% of COVID-19 tests are returning positive. In Alabama, Mississippi, and Oklahoma, the positive rate is over 30 percent. Many of the coronaviruses circulating in the community increase the likelihood of breakthrough infections.

This is most likely in tight working spaces, parties, restaurants, stadiums, and other close-knit situations. Breakthrough infections are also more likely to occur among health care workers who are in frequent contact with infected patients.

For unknown reasons, national CDC data show that women account for 63% of breakthrough infections. Some small studies have identified women as the majority of groundbreaking cases.

Vaccines reduce the robustness of the immune response among the elderly, and the likelihood of breakthrough infections increases with age. Of the breakthrough cases followed by the CDC, 75% occurred in patients aged 65 years and older.

Immunodeficiency or underlying illnesses such as high blood pressure, diabetes, heart disease, chronic kidney disease, lung disease, and cancer increase the likelihood of breakthrough infections and can lead to severe COVID-19. For example, fully vaccinated organ transplant recipients are 82 times more likely to develop a breakthrough infection, and one study found that the risk of hospitalization and death after a breakthrough infection was higher than that of the vaccinated general population. It was 485 times higher.

How do variants like Delta change things?

Researchers have developed today’s vaccine to prevent early strains of the SARS-CoV-2 virus. Since then, new mutants have emerged, many of which are excellent at dodging antibodies produced by currently licensed vaccines. Existing vaccines are still very effective against these mutants to prevent hospitalization, but they are less effective than previous mutants.

According to Public Health England, two doses of the mRNA vaccine were only 79% effective in preventing symptomatic disease with delta, compared with 89% in the previous alpha mutant. A single dose provided only 35% protection against Delta.

By July 19, approximately 12.5% ​​of the 229,218 delta mutation cases across the United Kingdom were among fully vaccinated people.

In Israel, where vaccination rates are high, complete vaccination with the Pfizer vaccine can be as effective as only 39% to 40.5% in preventing delta mutation infections of any severity, from an initial estimate of 90%. I am reporting.

Israeli findings suggest that within six months, the effectiveness of the COVID-19 vaccine in the prevention of infections and symptomatic diseases will decline. Fortunately, however, the vaccine remains highly effective in protecting against hospitalization (88%) and severe illness (91.4%) caused by the currently predominant delta mutants.

So how long does the vaccine last?

As of the end of July 2021, 49.1% of the US population, or just over 163 million, has been fully vaccinated. Almost 90% of Americans over the age of 65 have been vaccinated at least once.

Scientist models suggest that vaccination could have saved about 279,000 lives in the United States and prevented up to 1.25 million hospitalizations by the end of June 2021.

Similarly, in the United Kingdom, approximately 30,300 deaths, 46,300 hospitalizations and 8.15 million infections may have been prevented by the COVID-19 vaccine. In Israel, high immunization rates are believed to have reduced cases by 77% and hospitalizations by 68% from the country’s pandemic peak.

Throughout the United States, only 150 of the more than 18,000 deaths from COVID-19 in May were fully vaccinated. This means that almost all COVID-19 deaths in the United States are among those who remain unvaccinated.

As Anthony Fauci said, the United States is becoming “almost like two Americas,” divided into vaccinated and non-vaccinated. People who have not been fully vaccinated with COVID-19 are at risk for the coronavirus, which has killed more than 600,000 people in the United States so far.

The writer is a project coordinator and staff scientist at Vanderbilt University Medical Center at Vanderbilt University. ET Health World