Unknown COVID Vaccine Side Effects May Appear After Millions Immunized—But Benefits Outweigh Risks

The potential rare, and long-term side effects of COVID vaccines may emerge—if they do at all—after millions of people are immunized, experts have told Newsweek. However, they stressed the benefits of getting vaccinated against a virus that has killed over 1.4 million people worldwide and is still raging in many countries by far outweighs the risks.

COVID vaccines by pharmaceutical and biotechnology companies Pfizer/BioNTech, Moderna, and AstraZeneca are the current front-runners for roll-out in the West. Phase 3 trials have found the former two to be 95 percent effective against COVID, with the latter 62 percent effective after two full doses, and 90 percent after half a dose and a full dose.

On Wednesday, the United Kingdom made history by becoming the first Western country to licence a COVID vaccine, after its independent medicine regulator gave the green light for the Pfizer vaccine to be rolled out. The government expects to start vaccinating high-risk groups from early next week. In the U.S., Pfizer and Moderna have applied to the U.S. Food and Drug Administration for their COVID vaccines to be authorized for emergency use. It is hoped distribution may start in December.

What are the side effects of the Pfizer/BioNTech, Moderna, and AstraZeneca COVID vaccines?

The side effects for any vaccine fall into two categories, the mild, short-term effects that fade within a few days, sore arms, and potential severe side effects, like allergies or autoimmune diseases.

Generally, most side effects show up within two months after a person is immunized, meaning anything severe would have likely shown up in trial COVID vaccine participants by now, experts told Newsweek.

The short-term side effects for the Moderna vaccine include soreness at the site of injection, fatigue, muscle and joint pains, and headaches. Pfizer/BioNTech have reported fatigue and headaches as common side effects. AstraZeneca's shot can trigger similar side effects to Moderna and Pfizer's, as well as feeling feverish. These are a welcome sign that the body's immune response has kicked in.

What do we know about the long-term, or rare side effects?

Experts told Newsweek that it is possible that long-term or rare side effects may emerge after millions of people are immunized. These won't be known if and when the FDA or other health bodies authorize the vaccines, said William Moss, director of the International Vaccine Access Center Executive at the Johns Hopkins Bloomberg School of Public Health. That is why scientists, manufacturers and officials will keep an eye on side effects after vaccines are rolled out.

Howard K. Koh, former assistant secretary for health under President Barack Obama professor of the practice of public health leadership at the Harvard T.H. Chan School of Public Health said: "Monitoring and reporting those outcomes are critical to assuring trust and confidence in any vaccine."

covid vaccine, stock, getty
A stock image shows a vaccine being prepared for injection. COVID vaccines will soon be rolled out in the U.K. Getty

But by definition, rare side effects are just that, "rare," said Alessandro Sette, professor at the Center for Infectious Disease and Vaccine Research at La Jolla Institute for Immunology.

And it may be difficult to identify whether a problem is due to a vaccine, or if a person has fallen ill for an untreated reason. "Some adverse health effects seen may be due to coincidence and not vaccine-associated," said Professor Peter Chin-Hong an infectious disease specialist at UC San Francisco.

Al Edwards, associate professor in the pharmacy department at the University of Reading, U.K., said: "no-one ever stops monitoring the safety of medicines—all medicines not just vaccines—even after trials end and rollout starts. We don't generally expect any long-term side effects of vaccines."

It is also important to remember that the safety thresholds for vaccine approval are higher than other medical interventions, such as drugs, because they are being put into people who are healthy.

Edwards went on: "There are still 'unknown unknowns' and could be surprises but generally speaking, vaccines have never been safer than they are now because we are so much better at the advanced manufacturing needed to make them clean, controlled, pure and very refined in composition, storage, distribution and administration."

Catching COVID is more risky than getting a vaccine

The academics who spoke to Newsweek were emphatic that the benefits of getting a COVID vaccine far outweigh the potential risks.

Edward Hutchinson, a scientist at the Centre for Virus Research at the U.K.'s University of Glasgow, said: "Unless you are part of a clinical trial, if you ever get a vaccine it was licensed because its benefits were shown to outweigh its risks. When you make a choice about vaccination for yourself or your family, it is really important to remember that there are real risks that come with choosing not to get vaccinated, and these are likely to be much, much greater than any risk from having the vaccination.

"We now know that the risks from having these COVID vaccines are so small they didn't cause serious problems when they were given to many thousands of volunteers. On the other hand, we know that the risk of catching SARS-CoV-2 [COVID] is currently very high."

Even those not at risk of developing serious COVID, such as the young or those without underlying health conditions such as diabetes or heart problems, should consider getting vaccinated.

"If you have a mild dose of the virus you could end up passing it on to someone else and making them seriously, even fatally ill. Finally, and this is important, do you want to live like this forever? Vaccination is the only way that we can control the spread of this disease while living our lives normally again," said Hutchinson.

His comments comes at a time when COVID is burning through the the U.S., with experts forecasting that U.S. may be hit by the equivalent of a 9/11 per day by Christmas in terms of deaths. Already, over 270,000 people in the U.S. have died.

Moss said: "Given that we are in the midst of a pandemic that is not under control in the United States, and this is a potentially deadly infection, I think it is wise to get the vaccine as soon as it becomes available given the efficacy data. In my view, the benefits outweigh the risks, particularly for those at high risk of infection and severe disease who will be the first to receive the vaccines."

Professor Prakash Nagarkatti, an immunologist at University of South Carolina, held a similar view. "The vaccine should be taken as soon as it is offered to you especially if you are in the vulnerable population. The more number of people taking the vaccine, the better is the spread of herd immunity which can eradicate COVID-19 so that we can lead a normal life again," he said.