"Disinfectants’ efficacies and safeness to destroy or control the growth of viruses also come under the spotlight"
Amidst the pandemic, COVID vaccines have been the hottest topic around the world. Using disinfectants to keep our environment safe and clean has become part of our daily routine, therefore, disinfectants’ efficacies and safeness to destroy or control the growth of viruses also come under the spotlight. By comparing the mechanism of action of vaccine and how disinfectants work in killing the viruses, we know that disinfectants that are effective on SARS-CoV-2 shall also be effective against all variants identified by World Health Organization (WHO). Here is what you need to know about disinfectants.
How do vaccines work?
After we have been exposed to pathogens such as viruses, our immune system responds by producing antibodies, proteins that circulate in the blood and throughout the body. They quickly label viral cells and capture the viral antigen released. Immune cells are awakened to fight off the viruses attacking our body. The immune system also memorizes the threat it has defeated, such that it can recognize and respond more efficiently if it encounters the same threat again.
Now our SARS-CoV-2 mRNA vaccines are mimicking this process, based on incorporating the genetic code (mRNA) of the specific viral spike proteins, which are uniquely found on the surface of coronavirus. They inject the genetic code of the targeted spike protein into the human body, which triggers our immune system to recognize it as a foreign substance. Our immune cells use the incoming code to produce the harmless spike proteins that are identical to those produced originally by the viruses. Our immune system then produces complementary-shaped antibodies and activates other immune cells to fight against the virus after being triggered. These viral cells we encounter after vaccination are recognized and labelled with the lock and key model for destruction. This act as the “trial run” to prepare our immune system to produce the viral-binding antibodies, minimizing our chances of experiencing disease symptoms and hospitalization.
Viruses do mutate (change of genetic materials) overtime when they replicate. With various variants of SARS-CoV-2 spreading across the world, WHO has listed a total of 5 Variants of Concern, Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2) and Omicron (B.1.1.529), due to the fact that they demonstrated to be associated with one or more of the followings,
- Increased transmissibility or detrimental change in COVID-19 epidemiology;
- Increased virulence or change in clinical disease presentation;
- Decreased effectiveness of public health and social measures or available diagnostics, vaccines, therapeutics.
Worryingly, some variants of concern even show resistance against approved SARS-CoV-2 vaccines. In particular, the latest omicron strain BA.2 seems to have caught public attention with its even higher infection rates reported in many countries, especially in Hong Kong, reaching 1,000,000 cases and causing more than 7,000 fatalities by March 2022. But what has been changed?
Each of the strains involves mutations of spike proteins at multiple locations independently, whereas alpha, beta and gamma strains share one of the key mutations, N501Y. Delta strain also has P681R and L452R mutations at different spike proteins to increase its viral replication rate and surpass immune mechanisms. Omicron strain even have more spike mutation such as D614G that increase its infectivity and virion stability. The growing concern about the effectiveness of vaccines against different SARS-CoV-2 variants has encouraged more research on the risks of increased severity, reinfections and the understanding of asymptomatic transmission associated with Omicron strain.,
What about disinfectants?
Cleaning and disinfection are commonly adopted as the key infection control measures to prevent the spread of the COVID-19 virus. Coronavirus (SARS-CoV-2) is an enveloped RNA virus protected by a lipid bilayer envelope formed by fatty molecules called phospholipids. The membrane protects and holds the genetic material of the virus. These enveloped viruses can be killed or inactivated by destroying the integrity of the protective membrane, thereby, preventing them from infecting our healthy body cells. The good news is most common disinfectants do not effect by recognizing the antigens nor the genetic material of the pathogens, however, it work via structural denaturation, oxidation or clumping/coagulating of the pathogens. The mutant (i.e. the change of spike proteins’ genetic code) of SARS-CoV-2 has not changed the general physical features of the virus (e.g. the easy-to-break protective envelope), hence the disinfectants are effective on SARS-CoV-2 shall also be effective against all variants.
To conclude, immunity developed by vaccination relies on spike protein recognition and is highly dependent on the genetic makeup of the virus protein. In contrast, disinfectant works differently. Disinfection works by chemically eliminating the virus by targeting virus structure as a whole, i.e. a non-selective attack. In fact, the difficulty of killing a virus depends on its physical features, which is irrespective of mutations. The very similar contact time of different variants indeed indicates that they have similar susceptibility to the disinfectant. Luckily, according to The United States Environmental Protection Agency (EPA), all our existing disinfection strategies are appropriate and effective against all SARS-CoV-2 variants.
As the COVID-19 pandemic rages on, we shall stay vigilant and continue practicing hand hygiene as well as hard-surface cleaning and disinfection in order to prevent possible transmission of COVID-19 and protect everyone and the community with a safe environment.
 WHO: Tracking SARS-CoV-2 variants, https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/
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