What did the first active COVID-19 trial reveal?

A child passes the National COVID-19 Memorial Wall on the Banks of the River Thames on March 27 in London, England. (Xinhua News Agency reporter Li Ying/photo)

On March 31, 2022, the journal Nature Medicine published the results of the world's first trial of active infection with the human coronavirus.

A team led by Christopher Chiu, an infectious disease scientist and Chinese professor at Imperial College London, completed the study with the support of pharmaceutical company Open Orphan and the UK Department of Health and Social Security (DHSC). The trial began in 2021 with 36 volunteers, with an average age of 22 years (18-29), who were in good health, belonged to the low-risk group of covid-19, had not been infected with COVID-19, and had not been vaccinated against any COVID-19. In the end, seroconversion in 2 volunteers was excluded from the study, and valid data from the remaining 34 people were included in the study. Meanwhile, the virus infected by the volunteers was the original strain (SARS-CoV-2/human/GBR/484861/2020), which was extracted from a COVID-19 patient early in the covid-19 epidemic and did not show any significant mutations.

The first result was that none of the deaths were fatal, and the infected people showed mild to moderate symptoms without any severe illness. According to PCR test results, only 18 people (53%) were infected with the new crown virus, and the incubation period (from initial exposure to the virus or early symptoms) was an average of 42 hours. From the overall data, even if exposed to the new crown virus, 47% of people are not infected, indicating that the human body itself has a strong immunity against the new crown virus. Coupled with the fact that no one has died, it can be said that the young adults have won the attack on the new crown virus. Of course, the old, weak, sick and disabled, especially those with underlying diseases, are not included in this conclusion.

Secondly, judging from the time of infection and the recovery, the new crown virus does not cause any serious sequelae. Although an infected person can still detect an active virus from the body for up to 12 days after infection, the lower the viral load, the less it affects people.

In assessing sequelae, volunteers were isolated individually for at least 14 days before leaving after meeting discharge criteria, and the researchers followed them up over the following year to assess the sequelae of COVID-19 infection. In terms of common olfactory abnormalities and the after-effects of loss of smell, when the viral load in the nasal cavity peaked, 15 people (83%) developed olfactory abnormalities or lost their sense of smell, and 9 (50%) lost their sense of smell completely. By day 28 after infection, 61 percent still had varying degrees of olfactory impairment; by day 180, 28 percent had not fully recovered their sense of smell. After this, only 1 person still had an olfactory disorder.

However, according to other studies, the patient's sense of smell can be restored after one year. Moreover, there are no more than two hundred theories about the sequelae of the new crown, which lacks both scientific basis and misunderstanding. The timing of sequelae has different criteria in different countries. The U.S. Centers for Disease Control and Prevention (CDC) standard is that symptoms that persist 4 weeks or more after infection with COVID-19 are called sequelae. The UK standard is to extend to 12 weeks later, and within 12 weeks is classified as a symptom of the new crown infection period.

Even other sequelae, such as feeling tired as the most common, recover quickly. According to the Danish study, the proportion of people who recovered from infection felt fatigue on a regular basis was 11.1%, but it dropped to 7.5% at 9 months and then to 3.3% in a year. A Spanish study that followed recovered covid-19 patients (who were diagnosed with pneumonia in severely ill COVID-19 patients) showed that at week 4, 28.3% of the recovered had symptoms of post-COVID-19 syndrome, and by 12 weeks the proportion dropped to 8.3%.

According to these studies, the vast majority of sequelae go away 1 year or more after an infected person recovers.

On the other hand, the results of the world's first trial of active infection with human new coronavirus also provide clues for the prevention and treatment of new crown. In terms of symptoms, 88.9% of the 18 infected people developed mild to moderate cold-like symptoms such as nasal congestion, rhinitis, sneezing, sore throat, etc., and 39% had a fever (greater than 37.8 ° C), and these people had other symptoms, such as headache, muscle ache, fatigue, olfactory impairment and loss.

The results of the world's first test of active infection with the new crown virus in humans also provide clues to epidemic prevention, such as nucleic acid testing, throat swab testing should be initiated as soon as possible. Because, this study shows that volunteers can test positive with a throat swab 40 hours (1.67 days) after they are infected, and can only test positive by a nasal swab after 58 hours (2.4 days).

However, in terms of viral load, the virus peak in the nasal cavity is higher than the virus peak in the throat, with a peak of 8.87 log10 copies/ml (95% CI 8.41-9.53) in the nasal cavity after infection, and a peak virus peak of 7.65 log10 copies/ml (95% CI 7.39-8.24) in the throat. Therefore, early detection can be done by throat swabs, and more accurate tests can be done by nasal swabs because of the higher viral load in the nasal cavity.

This study also verifies whether some of the current epidemic prevention practices need to be adhered to and improved. The average incubation period for infection in this study was 42 hours, which is much shorter than the current estimate of 5-6 days for the average viral infection. In addition, the surviving virus can still be detected in some volunteers at 9 and 12 days after infection, which is in line with the 14-day isolation period currently in place.

Of course, the results of the world's first trial of active infection with the human coronavirus were only derived from healthy young people. In view of this, a different strategy for epidemic prevention and control has also been proposed. Protection is needed for the elderly and the weak and the chronically ill, while the able-bodied young and healthy do not need to panic too much, but the necessary measures also need to be implemented, such as wearing masks, washing hands frequently, not gathering, etc.

Zhang Tiankan