Safety, efficacy, side effects and novel technology: Everything you need to know about the first vaccine against the deadly virus

How does the vaccine work?

The Pfizer-BioNTech and Moderna vaccines contain a molecule called RNA, which encodes the instructions for building a viral protein called "spike" — the protein that gives the novel coronavirus its spiky appearance and enables it to infiltrate and infect human cells. The RNA is injected into a muscle, entering the cells in the injection area, and causing them to produce numerous copies of the viral protein. A similar process of replication occurs when the virus infiltrates a cell, except that in the vaccine’s case, only one protein is manufactured by the cells, rather than the entire virus.

Within a short time, our immune system detects that something is "wrong." It picks up on the fact that its cells are expressing a foreign protein they normally shouldn't, and it takes a snapshot of that protein's structure. Later, if the vaccinated individual is exposed to a real virus, the immune system will recognize it immediately — and act against it. This allows vaccinated people to skip a long learning phase that would take about two weeks from the moment of infection with a real virus. Through vaccination, our body learns to recognize the virus without having to deal with a viral attack at the same time.

How does the mRNA vaccine work? Illustration: Noa Katz, based on a tweet by Zavén Sargsyan

How does the mRNA vaccine work? Illustration: Noa Katz, based on a tweet by Zavén Sargsyan

What is the difference between the Pfizer and Moderna vaccines?

Both vaccines are based on a similar technology, have similar efficacy, and are administered in two doses. The interval between the doses is three weeks for the Pfizer vaccine and four weeks in Moderna’s case.

The main difference between the vaccines is in their storage requirements, since the Moderna vaccine is much simpler to store and distribute. The Pfizer vaccine has to be kept at -70 degrees Celsius. The company has developed special packages to facilitate storage for up to 30 days. These packages keep the vaccines cold as long as they are filled with dry ice. The vaccine can be refrigerated at 2-8 degrees Celsius for five days, and can be left outside the refrigerator for up to two hours. The vaccine also needs to be diluted with a salt solution (saline) before use.

By contrast, the Moderna vaccine can be stored in standard freezers, at -20 degrees Celsius, for at least six months. It can also be refrigerated for 30 days and be kept at room temperature for up to 12 hours. It does not need to be diluted prior to its use.

Are the vaccines expected to end the pandemic?

It is very likely that the vaccines will spell the end of the pandemic, but their approval doesn't mean that we will be returning to normal any time soon. That will take at least a few more months. The first obstacle is making the vaccines widely available: It will take time until there are sufficient doses for the entire population of the country and the world. Initially, the vaccines will help protect the most vulnerable populations and critical healthcare workers. Until the majority of the public is vaccinated, we will have to continue employing the now-familiar protection means of - physical distancing and masks.

Another setback is that it takes time for each vaccinated person to develop immunity. The vaccine is administered in two doses, about one month apart. A person can be regarded as immunized only two weeks after the second dose.

It is not clear yet for how long the vaccine provides immunity  to COVID-19. Immunity may decline with time, so booster shots may be needed to maintain the immune memory and to ensure we are protected from the virus. It also remains to be seen whether the vaccine only  protects against severe illness or also prevents people from contracting COVID-19 and transmitting it to others, without getting sick themselves. As long as scientists are not certain the vaccine prevents infection, everyone will have to keep taking precautions, even after being vaccinated. Nevertheless, it is very likely that the vaccine does prevent infection, or at least that it reduces the chances of infection, because animal trials indicate that immunized monkeys became resistant to infection and do not transmit the virus.

In any case, it is hard to believe that the vaccines will lead to the extinction of such a common virus, which has spread across the world. It seems that the novel coronavirus, SARS-CoV-2, is here to stay, and we will have to keep vaccinating people against it, as we do to protect against other viruses.

How do we know the vaccines work?

Before being tested in humans, the vaccine was tested in animals, especially monkeys. Scientists tried to infect immunized monkeys with COVID-19, but the monkeys did not catch the disease. In the second phase of the clinical trials in humans, scientists investigated  vaccine efficacy indicators - the levels of antibodies in the bloodstream over time (four months, as of now), the antibodies’ ability to neutralize the virus in laboratory conditions and other indicators of immune memory.

Additionally, in the third and most comprehensive phase of the clinical trials, researchers recruited 44,0000study participants, who either received the active vaccine, administered to the intervention group, or a placebo, administered to the control group. The scientists followed up on each of the participants who got sick with COVID-19 and checked to see which group they belonged to. The results show that the vast majority of those infected were in the  placebo group. These findings suggest that the vaccine effectively prevents people from becoming sick. Over the next few months, we will find out whether the vaccine prevents people from getting infected. That is a very likely outcome.

How long is the vaccine good for?

As the trials with the COVID-19 vaccine started only a few months ago, it's impossible to determine exactly how long vaccine-induced immunity lasts. However, the experiments in humans and animals showthat antibody levels remain high for at least four months after receiving the vaccine, indicating a strong immune response. We may have to get another booster dose after one year, as we do with other vaccines.

How do we know the vaccine is safe?

The Pfizer vaccine was administered to some 22,000 people in the past few months and no severe side effects were found. Authorization was granted after one-half of the clinical study participants received their second vaccine dose — providing sufficient time to identify any unusual side effects. The participants are still being monitored to ensure that no unexpected side effects emerge in the future.

Who is the vaccine not recommended for?

The Pfizer vaccine is approved for use in individuals 16 years of age or older. It is not intended for use in younger children and youth at the current time, because the trials did not include this age group. In addition, although there is no known cause to fear vaccinating pregnant or breastfeeding women, the vaccine has not been tested on these populations yet and therefore, there is no recommendation to do so. Due to two cases of allergic reactions to the vaccine in the UK, the current recommendation is that people with a history of severe allergic reactions (anaphylaxis) refrain from being vaccinated, to be on the safe side.

What are the known side effects?

The most common side effect is pain in the injection area (84 percent). Other common side effects are dizziness (62 percent), headaches (55 percent), chills (38 percent), joint pain (23 percent), and fever (14 percent). The risk of more severe side effects is less than half a percent, and no life-endangering side effects were found in the large-scale trial. Most of the participants reported experiencing side effects for up to one or two days, and mostly after the second dose. The side effects were less frequent in people over 55.

What about rare or long-term side effects?

As far as we know, these side effects should not exist. It's very rare for a vaccine to have side effects that appear long after it was given. However, science is about assuming less and testing more; therefore, the clinical trials are still ongoing and the volunteers who received the vaccines are being monitored for any side effects or complications.

So why aren't we waiting a year or two, until we can be sure? The reason is simple - the cost would be much too high. Although this may be the first approved vaccine based on  this technology, other trials of RNA technologies have been conducted in recent years and did not lead to any long-term side effects that should be a cause for concern. Furthermore, the virus causes many short-term complications, and, as time goes by, we are also seeing long-term complications, so it seems that any potential vaccination risks are significantly outweighed by the dangers of COVID-19.

I heard a scary rumor about the vaccine. How can I tell if I should believe it?

We will probably be hearing many rumors about the vaccine making the rounds over social media, messaging apps, and other media outlets. First, it's important not to get stressed out. Chances are that the more outlandish the rumor, the more baseless it is. Check reliable sources, consult with authorized health professionals, and do not make decisions based on unverified information under any circumstances. Remember, if a warning is of consequence, you will run into it in several places, such as news programs, science websites, Ministry of Health announcements, and others - not just in random WhatsApp messages.

Is the vaccine really better than catching the disease?

Absolutely! The vaccine is effective, has few side effects, and even if it turns out to induce just a short immune memory, we can get a booster shot next year. By contrast, the disease can cause pneumonia, an extended stay atthe ICU and even death - and not just for the elderly. Many recovering patients feel weak and have a hard time getting back to normal. If that's not enough, we don't even know whether being sick once prevents another infection. The virus has been around for only a year, so we don't know what are the long-term effects of the disease. Experiments conducted in tens of thousands of people show that by any metric, getting the vaccine is better than catching the virus.

Weren’t shortcuts taken in the development of the vaccine?

Vaccine development usually takes several years. A large part of that time is wasted on bureaucracy, fundraising, recruiting volunteer study participants, and waiting for regulatory bodies like the Food and Drug Administration (FDA) to check every step of the trials.

From the outset of the pandemic, it was clear that any exit strategy would require a vaccine. This is why any step of the process that didn't affect the safety and efficacy was shortened. Many governments, and chiefly the United States, invested billions of dollars in companies that showed potential to develop a vaccine within a reasonable timeframe. Additionally, some of the trial phases slightly overlapped their previous phases, and participant recruitment was simple, because people were lining up to join the clinical trials.

Finally, one factor causing much of the delay in the development of new vaccines is waiting for enough participants to catch the disease, so that the researchers can check to see which group they belonged to: The intervention group or the control group. Since we are in the midst of a pandemic caused by a highly infectious virus, this milestone was reached very quickly.

The only part in which a certain risk was taken was the timing of the emergency approval. A clinical trial should last about two years to identify long-term side effects. Since waiting that long would cost many human lives and cause significant suffering, the developers waited only two months after the second dose was given before submitting the vaccine for emergency approval. The trial isn't over, and the participants are still being monitored, but the vaccine was already approved to save lives. The risk is not high, and is definitely lower than the risks of catching the disease.

I heard that the vaccine damages fertility in women. Is this true?

Absolutely not. There is no biological reason for that to happen. The vaccine causes the body to produce antibodies against a small part of the novel coronavirus and they can only target that part. Furthermore, the viral infection  causes both the COVID-19 disease and the production of antibodies against the virus. If this rumor was based, we would expect women who recovered from COVID-19 to have reduced fertility - but this is not the case at all.

What about the Russian vaccine?

The Sputnik 5 vaccine, developed in Russia, has passed two phases of clinical trials and was approved for use without passing the third phase. This phase is being conducted in several countries worldwide, but the findings have not yet been published and checked by independent sources, so it is difficult to ascertain whether it is safe and effective.

The vaccine itself is based on a viral vector; this means that its developers took a virus that is not dangerous for humans and cloned instructions to build one of the proteins of the novel coronavirus into it. The engineered virus should infect cells in the bodies of the vaccine recipients and induce them to produce the protein. This is a well-known method that has been approved for use in humans and is considered safe. However, before the vaccine passes all three clinical trials phases and the results are inspected by an objective health authority, there is no way of knowing if it is safe and effective.

What about the Israel Institute for Biological Research (IIBR) vaccine?

The IIBR vaccine recently started the first phase of clinical trials , meant to test its safety. The IIBR states that the second phase, testing its efficacy, will be starting soon. This vaccine is also based on a virus that is not dangerous for humans, which was modified to contain the instructions for a viral protein. We will have to wait patiently to see whether this vaccine passes the clinical trials.