立即打开
南非的新冠病毒变种,有多“恶”?

南非的新冠病毒变种,有多“恶”?

Sy Mukherjee 2021年01月26日
此类突变具有实际意义,引发大众对现有疫苗是否仍旧有效的疑问。

对病毒来说,变异再正常不过。

新冠病毒的南非变种,又被称为501Y.V2毒株,似乎比疫情初期流行的中国和欧洲毒株更具传染性和可转移性。

南非新冠毒株之所以感染性强,是因为突变后影响了“刺突蛋白”这一新冠病毒用来渗透人体细胞的重要工具。突变或使病毒更易于传播,但还不清楚病毒的致命性是否也有所增加。到目前为止,美国还没有任何南非型新冠变异病例的报告。但随着时间的推移和监测的加强,情况或将改变。世界卫生组织(World Health Organization)的数据显示,南非毒株已经扩散到至少20个其他国家,包括英国、法国、瑞士、日本、奥地利和赞比亚。

新冠病毒的变异听起来很吓人,但变异是所有传染性病毒都会发生的事情。以流感为例,美国疾病控制中心(Centers for Disease Control)的数据显示,流感病毒就有四种不同的毒株,每种毒株还可以有自己的亚型,就像每种语言都会分流出不同的方言一样。

病毒毒株的多样性意味着疫苗也需要多样化。尽管部分生物制药公司正试图制造通用性的流感疫苗,但流感疫苗目前仍然无法做到年复一年不做任何更新、改变。病毒就像其他生物实体一样,适应着环境,发生着变化。因此,公共卫生部门必须密切关注病毒突变,以便在现有疫苗的基础上研发更有效的产品。

此类突变具有实际意义,引发大众对现有疫苗是否仍旧有效的疑问。对传染性的担忧持续发酵,1月25日,美国得到获批的两家疫苗生产商之一的Moderna公司宣布,其正在研制新的强化注射剂(booster shot)以应对南非的变种毒株。

Moderna公司的首席执行官史蒂芬•班塞尔在声明中说:“出于谨慎考虑,我们正利用mRNA平台的灵活性,研发一种新兴的候选疫苗强化剂,以应对在南非出现的新毒株,以及日后还可能出现的新的变异情况。目前,该强化剂已经投入临床试验,以检测其是否能够有效提高浓度,抵御新毒株。”

与所有和新冠有关的事情一样,现在就断言现有疫苗对变异病毒的有效性还为时过早。Moderna称,对于尤为特殊的南非变种和最开始在英国发现的新冠病毒变种,其疫苗都可以“至少提供一些保护”。

在疫苗对新毒株的有效性上,世界卫生组织传递出的信息一直很谨慎。该组织称:“就自然免疫或免疫源疗法而言,B.1.351毒株或501Y.V2毒株的突刺蛋白突变理论上有可能降低抗体对病毒的识别能力,但不能完全消除。这是因为,人类免疫系统将识别不止一个刺突蛋白所在的区域,而变异只能降低疫苗‘定向摧毁’突刺蛋白的有效率,并无法使疫苗的效力完全丧失。”

疫苗制造商深知这一点。某种毒株的流感疫苗可能对该毒株有60%的效力,但对另一种毒株就只有30%的效力。Moderna公司的疫苗对新冠原始毒株具有约95%的有效性,医学专家们希望,对南非和英国的新变种,Moderna的疫苗仍然能够达到70%以上的有效率。

令人担忧的是,该疫苗似乎不能产生足够强大的免疫反应——而免疫反应正是抵御病毒的关键。70%左右的有效率仍聊胜于无——这也是公共卫生部门坚持每个人都要注射流感疫苗的原因,就算将来某一天它的有效性大大降低;但毕竟“只有”70%了,因此,Moderna公司开始着手准备强化剂。

此外,还有一个问题:这些新冠病毒“后代”的致命性如何。英国首相鲍里斯•约翰逊最初表示,有“一些证据”表明,英国的新变种使新冠病毒更具致命性,但公共卫生部门和政府官员此后的说法要温和得多,警告称变异病毒的致命性仍然有很大的不确定性。

Moderna公司的举动是预防性的,现在要判断这些新的变种是否比以前的变种更致命还为时过早。截至目前,情况似乎并非如此。该公司认为,其基于mRNA的疫苗具有可塑性,通过底层技术,可以比其他类型的疫苗更快地生产、扩大规模,因此,应对更凶险的新冠病毒变种,Moderna公司具备足够的灵活性。

就算别无他法,至少这次疫情也突出了在面对未来潜在的传染病威胁时,做好准备有多么重要。(财富中文网)

编译:杨二一

对病毒来说,变异再正常不过。

新冠病毒的南非变种,又被称为501Y.V2毒株,似乎比疫情初期流行的中国和欧洲毒株更具传染性和可转移性。

南非新冠毒株之所以感染性强,是因为突变后影响了“刺突蛋白”这一新冠病毒用来渗透人体细胞的重要工具。突变或使病毒更易于传播,但还不清楚病毒的致命性是否也有所增加。到目前为止,美国还没有任何南非型新冠变异病例的报告。但随着时间的推移和监测的加强,情况或将改变。世界卫生组织(World Health Organization)的数据显示,南非毒株已经扩散到至少20个其他国家,包括英国、法国、瑞士、日本、奥地利和赞比亚。

新冠病毒的变异听起来很吓人,但变异是所有传染性病毒都会发生的事情。以流感为例,美国疾病控制中心(Centers for Disease Control)的数据显示,流感病毒就有四种不同的毒株,每种毒株还可以有自己的亚型,就像每种语言都会分流出不同的方言一样。

病毒毒株的多样性意味着疫苗也需要多样化。尽管部分生物制药公司正试图制造通用性的流感疫苗,但流感疫苗目前仍然无法做到年复一年不做任何更新、改变。病毒就像其他生物实体一样,适应着环境,发生着变化。因此,公共卫生部门必须密切关注病毒突变,以便在现有疫苗的基础上研发更有效的产品。

此类突变具有实际意义,引发大众对现有疫苗是否仍旧有效的疑问。对传染性的担忧持续发酵,1月25日,美国得到获批的两家疫苗生产商之一的Moderna公司宣布,其正在研制新的强化注射剂(booster shot)以应对南非的变种毒株。

Moderna公司的首席执行官史蒂芬•班塞尔在声明中说:“出于谨慎考虑,我们正利用mRNA平台的灵活性,研发一种新兴的候选疫苗强化剂,以应对在南非出现的新毒株,以及日后还可能出现的新的变异情况。目前,该强化剂已经投入临床试验,以检测其是否能够有效提高浓度,抵御新毒株。”

与所有和新冠有关的事情一样,现在就断言现有疫苗对变异病毒的有效性还为时过早。Moderna称,对于尤为特殊的南非变种和最开始在英国发现的新冠病毒变种,其疫苗都可以“至少提供一些保护”。

在疫苗对新毒株的有效性上,世界卫生组织传递出的信息一直很谨慎。该组织称:“就自然免疫或免疫源疗法而言,B.1.351毒株或501Y.V2毒株的突刺蛋白突变理论上有可能降低抗体对病毒的识别能力,但不能完全消除。这是因为,人类免疫系统将识别不止一个刺突蛋白所在的区域,而变异只能降低疫苗‘定向摧毁’突刺蛋白的有效率,并无法使疫苗的效力完全丧失。”

疫苗制造商深知这一点。某种毒株的流感疫苗可能对该毒株有60%的效力,但对另一种毒株就只有30%的效力。Moderna公司的疫苗对新冠原始毒株具有约95%的有效性,医学专家们希望,对南非和英国的新变种,Moderna的疫苗仍然能够达到70%以上的有效率。

令人担忧的是,该疫苗似乎不能产生足够强大的免疫反应——而免疫反应正是抵御病毒的关键。70%左右的有效率仍聊胜于无——这也是公共卫生部门坚持每个人都要注射流感疫苗的原因,就算将来某一天它的有效性大大降低;但毕竟“只有”70%了,因此,Moderna公司开始着手准备强化剂。

此外,还有一个问题:这些新冠病毒“后代”的致命性如何。英国首相鲍里斯•约翰逊最初表示,有“一些证据”表明,英国的新变种使新冠病毒更具致命性,但公共卫生部门和政府官员此后的说法要温和得多,警告称变异病毒的致命性仍然有很大的不确定性。

Moderna公司的举动是预防性的,现在要判断这些新的变种是否比以前的变种更致命还为时过早。截至目前,情况似乎并非如此。该公司认为,其基于mRNA的疫苗具有可塑性,通过底层技术,可以比其他类型的疫苗更快地生产、扩大规模,因此,应对更凶险的新冠病毒变种,Moderna公司具备足够的灵活性。

就算别无他法,至少这次疫情也突出了在面对未来潜在的传染病威胁时,做好准备有多么重要。(财富中文网)

编译:杨二一

For a virus, mutation is just a reality of life.

Just consider the South African variant of the coronavirus, somewhat inelegantly dubbed 501Y.V2 for now. This strain of the coronavirus (and there are plenty of coronavirus strains beyond the ones which cause COVID) appears to be far more contagious and transmissible than the Chinese and European strains that were prevalent in the early days of the pandemic.

The reason? The mutations in the South African strain affect the "spike protein," the essential tool that the novel coronavirus uses to infiltrate the body's cells. And those mutations appear to make it easier to spread, though it's unclear if it actually makes the virus deadlier. There haven't been any reported cases of this variant in the U.S. to date. But that could easily change with more time and robust surveillance, and the South African strain has spread to at least 20 other countries according to the World Health Organization (WHO), including the U.K., France, Switzerland, Japan, Austria, and Zambia.

As scary as a coronavirus mutation may sound, it's par for the course with any transmissible virus. Take the flu for example. Per the Centers for Disease Control (CDC), there are four separate strains of the flu virus, and those strains can have their own subtypes. It's sort of like how the same language may be spoken with different dialects.

But that biological diversity necessitates a diversity of vaccines. The flu isn't just one consistent vaccine from year to year (although some biopharmaceutical companies are attempting to create a universal influenza shot). Viruses adapt and change just as any other biological entity does. That's why public health official have to keep such a close eye on the contours of a mutation in order to facilitate more effective products that build on the existing ones.

Such mutations have practical implications and raise concerns over whether or not currently available vaccines would be as effective against them. Transmissibility worries led Moderna, which makes one of the two COVID vaccines currently authorized in the U.S., to announce on January 25 that it is working on a booster shot to deal with the South African variant.

"Out of an abundance of caution and leveraging the flexibility of our mRNA platform, we are advancing an emerging variant booster candidate against the variant first identified in the Republic of South Africa into the clinic to determine if it will be more effective to boost titers against this and potentially future variants," said Moderna CEO Stephane Bancel in a statement.

As with everything COVID-related, it's too early to say definitively how effective the current vaccines would be against a mutated coronavirus. Moderna believes its vaccine would provide at least some protection even against this particular South African COVID strain, as well as a different coronavirus mutation first identified in the U.K.

The WHO has been cautious in its messaging about vaccine efficacy against new strands. "In terms of natural immunity or immune-derived therapeutics, mutations in the spike protein of the B.1.351 or 501Y.V2 may, in theory, reduce, but not obliterate the recognition of the virus by antibodies. This is because, in practice, the human immune system will recognize more than a single region of the spike protein," writes the agency. "Mutations may reduce vaccine efficacy directed against the spike protein but will not obliterate their effects."

Vaccine makers have long known this reality. A flu vaccine may be 60% effective against one particular strain but just 30% effective against another. Moderna's vaccine is about 95% effective for the original coronavirus strain and medical leaders hope that it will still be at least 70% effective against new variants such as the South African and U.K. strains.

What's concerning is that the vaccine doesn't seem to produce quite as robust of an immune response, which is critical to warding off the virus. A an efficacy rate around 70% is still far better than nothing—after all, that's why public health officials insist everybody get a flu shot even if it's not very effective in a given year—but also explains why Moderna is preparing its booster shot.

How fatal these coronavirus offspring could be is another question. Prime Minister Boris Johnson initially said there was "some evidence" that the U.K. variant made the virus more deadly, but public health and government officials have tempered those claims since, cautioning that there's still a great deal of uncertainty about the strain's deadliness.

Moderna's move is precautionary and it's far too early to tell if these new variants are significantly more deadly than the previous ones. So far, that doesn't seem to be the case. And the company believes the malleability of its mRNA-based vaccine, which can be manufactured and scaled up faster than other types of vaccines due to its underlying technology, gives Moderna the flexibility to prepare for a more dangerous COVID variant.

If nothing else, the pandemic has underscored the important of preparation when it comes to potential infectious disease threats in the future.

最新:
  • 热读文章
  • 热门视频
活动
扫码打开财富Plus App