Will Covid-19 Kill the Handshake?

The handshake might date back to the 14^th century, when knights (骑士) and soldiers would extend their unclenched(松开的) right hands toward each other in greeting to show that they were carrying no weapons.

【小题1】 Or rather, its tendency for picking up and holding onto germs (细菌) from polluted surfaces, or from   our own eyes or noses when we have certain illnesses. Those germs can then be transferred into the hands of the people we greet, while we can pick up their germs. We then will probably touch our own eyes or noses or mouths, potentially sickening ourselves and restarting the cycle.

Now that a novel coronavirus is spreading fast, our hands are being cast in a new, doubtful light. 【小题2】 And lately, the Internet has been full of suggestions for socially acceptable ways to greet each other that don’t involve passing germs along unintentionally from one person to the next.

【小题3】 In fact, the tradition of shaking hands isn’t the only greeting to take a fresh look. A Maori tribe in New Zealand put the brakes on hongi, the traditional nose-to-nose hello. 【小题4】 Maybe people will stop making fun of the Hollywood air kiss, though it’s not a huge improvement health-wise.

COVID-19 is a real threat, and we shouldn’t take the warning lightly. We may, indeed, need to keep our hands to ourselves for the time being. But we’re not ready to send handshake into the dustbin of history. Humans long for making a physical connection with friends. For now, perhaps, a regretful smile and nod might work as a shared acknowledgment. 【小题5】

Nowadays, we are very worried about such COVID-19 variants as Delta and Omicron. To relieve our anxieties, we should have a look at our own cell and the original COVID-19 virus.

First of all, our cell isn’t stupid. If any virus wants to enter our cell, it must figure out a way for its spike (触手) to hold tightly to the spike on the cell’s surface. You can imagine this connecting as a secret handshake.

At the early stage, the COVID-19 virus figured out a way to connect to a specific spike on the surface of human cell, called ACE2. But the connecting wasn’t perfect. However, it was good enough to trick the ACE2 to let it in.

Once the virus was inside the cell, it kept copying itself in order to find more cells to infect. During this time, the immune (免疫) system started making antibodies to fight back. Some of those antibodies acted like little caps that stick to the ends of the virus’s spike. Once “capped”, the infection couldn’t move forward, and the body won!

But every time the virus copies itself inside a cell, it has the chance of changing its spikes slightly. Most of the variations are actually harmful to the virus. So these variants disappear. However, once the virus hits upon a set of variations that actually help the virus to connect more tightly to the cell or more quickly, a person’s cell gets infected more easily.

Then what about the antibodies? Aren’t they coming to save us again? Well, yes... and no.

Scientists found that a person who was infected with the earlier version of the virus may not be protected as well against these new variants. He still can be infected, again. However, the antibodies’ spikes come in different shapes, too. So even though some antibodies become less useful, others will get the job done—or at least, hold back the infection long enough so the body can make new antibodies that fit perfectly on the changed spike.

Hundreds of millions have rolled up their sleeves for the COVID-19 vaccine, but why haven’t they taken down their pants instead? What’s the science behind why we get most vaccines in our arm and does the injection site matter?

Muscles make an excellent vaccine injection site because muscle tissue contains important immune cells. The immune cells recognize the antigen (抗原), a tiny piece of a virus or bacterium introduced by the vaccine that stimulates an immune response. In the case of the COVID-19 vaccine, the immune cells in the muscle tissue pick up these antigens and take them to the lymph nodes (淋巴结). Injecting the vaccine into muscle tissue keeps the vaccine localized (局部的), allowing the immune cells there to sound the alarm to other immune cells and get to work. Once a vaccine is recognized by the immune cells in the muscle, these cells carry the antigens to lymph vessels, which transport the antigen-carrying immune cells into the lymph nodes. Lymph nodes, important part of our immune system, contain more immune cells that recognize the antigens from vaccines and start the immune process of creating antibodies.

Muscle tissue also tends to keep vaccine reactions localized. Injecting a vaccine into the muscle may result in local inflammation (红肿) or soreness at the injection site. If certain vaccines are injected into fat tissue, the chance of vaccine reactions increases because fat tissue has poor blood supply, leading to poor absorption of the antigens in the vaccines.

Yet another deciding factor in the vaccine injection site is the size of the muscle. Adults and children aged three and older tend to receive vaccines in their upper arm. Younger children receive vaccines in their thighs (大腿) because their arm muscles are smaller and less developed.

Another consideration during vaccine injection is convenience and patients’ acceptability. Can you imagine taking down your pants at a clinic with strangers around? Rolling up your sleeve is much easier and more preferred.

All things considered, when it comes to the COVID-19 vaccine, for most adults and kids, the arm is the preferred injection site.