Will the novel coronavirus break out again after the May Day holiday? Does the new virus strain cause conjunctivitis? One article explains it all!

From the surge in the number of positive COVID-19 infections starting at the end of last year to the decline in the number of infections and the gradual return of life to normal before the epidemic, many people have gotten over the haze of frequent nucleic acid tests and long-term mask testing.

But with the arrival of another holiday after the Spring Festival, many people can't help but start to worry about the arrival of the "next wave" of the new crown epidemic. Even some marketing accounts have begun to blatantly sell a certain brand of antipyretic drugs, which makes many people feel very frightened.

So will the epidemic really break out again in China? Do we still need to get vaccinated? If we look at the current situation rationally, we will naturally have the answer.

01

Immunity and variants

After the previous vaccination and the first wave of new coronavirus infections starting in December last year, the population's immune barrier has been established through "hybrid immunity" (vaccination and infection with the virus) . Therefore, after the number of infections has dropped, people's risk of illness is lower.

Although there is a lot of evidence that broad-spectrum and high-level neutralizing antibodies (which can directly prevent the virus from infecting cells) are obtained after infection, we have to face two realities:

1. The half-life of neutralizing antibodies will be shortened

2. XBB variants significantly reduce protection

Previous studies have found that although high levels of neutralizing antibodies can be obtained after infection, the neutralizing antibodies decay slowly in the first six months, and the half-life is almost halved after six months, which means a rapid decline. Even after nine months, only more than 70% of people have immunity to the new coronavirus when facing the original strain, and their antibody levels are not high.

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In addition, when facing XBB, even the neutralizing antibodies obtained after multiple doses of vaccine or even infection after multiple doses of vaccine have their neutralizing activity against the XBB variant reduced by dozens of times.

Therefore, during the period from December to now, the antibody level may have declined. If the XBB variant really strikes, the large-scale movement of people will inevitably make it difficult for many people's existing immunity to prevent XBB infection.

02

"Arcturus" variant

To make matters worse, the XBB variant has many substrains. For example, the spread of XBB in the United States was already staggering, and then XBB.1.5 quickly replaced XBB to become the dominant strain; just when many people thought that XBB.1.5 was the end of the new coronavirus, XBB.1.16, named "Arcturus", appeared.

According to GISAID data, in the first week of March 2023, XBB.1.6 accounted for only 0.5% of the world, but by the first week of April, this figure had soared to 4.2%.

XBB.1.5, which had previously been firmly in the top spot in the United States, also encountered a strong enemy. According to US monitoring data, XBB.1.16 accounted for 10% of new cases in less than two months, and this proportion is still rising.

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The reason why XBB.1.16 can rise so quickly may be that it is more contagious than previous XBB variants and substrains. A preprint that has not been peer-reviewed believes that XBB.1.16 is 1.27 times more contagious than the original XBB variant and 1.17 times more contagious than XBB.1.5.

However, the good news is that there is no sign that the severity of XBB.1.16 infection will increase. The "childhood conjunctivitis" problem that worried many parents before was actually only mentioned in a report from India, but it was impossible to distinguish whether it was related to the symptoms caused by spring pollen, and there were very few cases.

03

Cellular immunity of vaccines

Although many people hope that the XBB variant will not enter the country, unfortunately, not only XBB, but also XBB.1, XBB.1.5, and XBB.1.16 have already quietly entered the country.

According to the "National Novel Coronavirus Infection Epidemic Situation" information released by the Chinese Center for Disease Control and Prevention on April 22, from September 26, 2022 to April 20, 2023, there have been 530 XBB variants or substrains of the new coronavirus variants reported in my country, and they accounted for more than 30% of the national monitoring data in the past week.

In the face of multiple variants of Omicron, do we still need to get vaccinated?

Of course it is necessary.

Although the humoral immunity (neutralizing antibodies) brought by vaccination is no longer sufficient to provide effective protection against Omicron variants, especially substrains such as XBB, previous studies have found that the impact of variant escape on T cell immunity is far less than humoral immunity, and even inactivated vaccines can provide good protection by covering more viral targets.

This also explains why vaccination can effectively prevent severe illness and death when antibodies are insufficient. Therefore, for eligible people, booster doses are still very necessary, especially during this period.

04

summary

Although people's immunity gradually decreases over time and the XBB variant of the new coronavirus has spawned substrains with stronger transmission capabilities, vaccines can still enhance immunity to reduce the risk of severe illness and death, and are a safer option than natural infection.

Therefore, if you are worried about the possibility of infection and serious conditions after the holidays, the best way is still to protect yourself in crowded areas (wearing masks properly, washing hands frequently, indoor ventilation, etc.) and get booster doses of vaccine as soon as possible if you meet the conditions, especially for more vulnerable elderly people and people with underlying diseases.

Of course, individual vaccination can improve their own immunity level, but if you want to consolidate the immune barrier, more people need to act together.

Author: Shao Yinan, popular science creator

Reviewer: Tang Qin, Director of the Science Popularization Department of the Chinese Medical Association

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