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How COVID-19 vaccines work, why we need them

A little more than a year ago we started hearing that a new coronavirus was making people sick in China and might spread around the world. It did just that, making 2020 the hardest year many of us have known. It has felt like the longest year we’ve ever known, too.

But our doctors and medical scientists have learned a lot about the SARS-CoV-2 virus that causes COVID-19, how to keep us as safe as possible, and how to stop the pandemic. A few weeks ago, people started getting vaccinated against COVID-19. The pandemic isn’t over yet, but having several vaccines in use already, and more on the way, is remarkable and very encouraging.

When a pathogen (a germ that causes disease) enters our bodies, our immune systems fight back with customized cells called antibodies designed to “fit” that specific germ. The immune system “remembers” so that if the same pathogen returns it can recognize the invader and quickly bring up the right antibodies. If the invader isn’t recognized, the immune system must adapt an existing antibody or design a new one. It’s a race against time. If the germs win by reproducing faster than our bodies can create the right weapons, we can become very ill, even die.

Doctors and scientists know a lot about this process from dealing with diseases such as measles and influenza, so they have been able to develop and test COVID-19 vaccines and determine that they are effective and safe in a relatively short time. Vaccines may look like the real virus or may use small parts of it but are safe because they are not able to reproduce and cause disease. COVID vaccines “look like” SARS-CoV-2 to the immune system, which makes antibodies to “fit.” When the real COVID virus appears, the immune system is ready to fight it.

A disease outbreak that becomes a pandemic (spreads world-wide) won’t stop until it runs out of people to infect. This can happen naturally when enough people successfully fight it off and become immune. But this “herd” immunity comes at a terrible cost in human lives and misery. Vaccines are the only way to reach herd immunity quickly enough.

Everyone’s immune response is different because of past infections, genetic differences, immune deficiencies, age, or lifestyle factors such as smoking. No vaccine works the same for everyone and none are 100-percent effective. However, the Moderna and Pfizer vaccines currently being used and the Johnson & Johnson vaccine now under review have been very effective at preventing serious disease and hospitalizations.

Side effects may include arm soreness, aches, fever, and generally feeling “sick” for a couple of days. Unpleasant, but far less so than a severe case of COVID-19. They indicate that the vaccine is working, which is why the second dose often has more side effects as it kicks the immune response into high gear. (Having slight or no side effects doesn’t mean it’s not working.) To reduce pain from the shot, apply a cool wet washcloth and move your arm around. Drink plenty of fluids and dress lightly to reduce fever discomfort.

A few people have had severe allergic reactions (anaphylaxis) to these vaccines. You are unlikely to experience this yourself, but just to be safe you should be monitored for 15 minutes after getting your vaccine in case you need immediate treatment. If you have a milder reaction such as hives or wheezing, ask your doctor or other health care provider for advice.

We know a lot about COVID-19 but still have many questions. It takes time to learn how long immunity from COVID infections and vaccines lasts and whether boosters will be needed.

We need more studies to find out if the vaccines are safe for certain groups, including pregnant and breastfeeding women, children, and people with immune deficiencies or autoimmune conditions. We need to learn whether the vaccines prevent COVID-19 completely or if vaccinated people can still pass the virus on to others. We also must understand that COVID-19 is a moving target. Viruses are good at mutating, and some mutations can spread more easily or make people sicker.

The pandemic will end when enough of us are immune and the virus can’t find new people to infect. We don’t know how many because it depends on the effectiveness of vaccines, the rise of new virus variants, and what we all do. It takes time to build up immunity after getting the vaccine. We don’t know how long immunity lasts, and not everyone will or can take the vaccine.

This is why, after we get vaccinated, we must keep doing the things that we know help: wearing masks, social distancing, avoiding crowds and indoor gatherings, and washing our hands.

Let’s end COVID!

Michael Heyd, a retired medical librarian from Fairfield Township, spent more than 40 years searching the professional literature for doctors, nurses, educators and other staff at The Williamsport Hospital/Susquehanna Health. He is a member of Let’s End COVID, a group of concerned people in Northcentral PA working to overcome the COVID-19 pandemic through education, outreach and mitigation.

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