Global COVID-19 vaccine summary: Side effects
Written by Minseo Jeong on March 22, 2021 — Fact checked by Alexandra Sanfins, Ph.D.
Currently, in various areas of the world, 13 COVID-19 vaccines have been authorized for use. In this feature, we look at the types and their reported side effects.
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As the global effort to produce vaccines that can curb the COVID-19 pandemic forges ahead, headlines continue to highlight development breakthroughs and safety concerns.
This article summarizes the known side effects of the 13 authorized vaccines and provides insight into risks that researchers are still investigating.
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Currently authorized COVID-19 vaccines
The table below gives an overview of the 13 authorized vaccines, categorized by type, based on how they function. It also shows their efficacy.
Each of the following vaccines has received use authorization in at least one country.
Name Manufacturer Type of vaccine Efficacy rate BNT162b2Pfizer-BioNTechmRNA95%mRNA-1273ModernamRNA94.5%Ad26.COV2.SJanssen (Johnson & Johnson)Viral vector66%AZD1222Oxford-AstraZenecaViral vector81.3%Covishield*Serum Institute of IndiaViral vector81.3%Ad5-nCovCanSinoViral vector65.28%Sputnik VGamaleyaViral vector91.6%CovaxinBharat BiotechInactivated80.6%BBIBP-CorVSinopharm (Beijing)Inactivated79.34%Inactivated (Vero Cell)Sinopharm (Wuhan)Inactivated72.51%CoronaVacSinovacInactivated50.38%RBD-dimerAnhui Zhifei LongcomProtein subunitUnknownEpiVacCoronaFBRIProtein subunitUnknown
* Covishield is the Oxford-AstraZeneca vaccine produced for India.
Common side effects
Vaccines allow the body to build immunity by activating T and B lymphocytes, cells that, respectively, recognize the targeted virus and produce antibodies to combat it.
A vaccine cannot cause COVID-19. No vaccine contains a complete form of the virus responsible for this illness.
While their body builds immunity, it is normal for a person to experience minor side effects.
According to the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO), common side effects of a COVID-19 vaccine include:
- a fever
- body aches
A person might also experience side effects around the injection site, which is usually the upper arm. These might include swelling, pain, redness, an itchy rash, and other mild forms of irritation. People sometimes refer to this issue as COVID arm.
Health authorities recognize that each of the 13 authorized COVID-19 vaccines can cause side effects. These are often mild and last for only a few days. They are not unexpected.
Every vaccine facility in the United States has to report specific post-vaccination symptoms, known as adverse events, to the government’s Vaccine Adverse Event Reporting System (VAERS). Individuals can also submit reports through the VAERS portal.
The Food and Drug Administration (FDA), CDC, and other regulatory agencies are closely monitoring VAERS to scrutinize the safety of the vaccines used in the U.S.
Similar systems are in place in other countries. In the United Kingdom, for example, the scheme is called Yellow Card. The European Union asks people to report suspected side effects to their healthcare practitioners or fill out dedicated online forms.
Allergic reactions and anaphylaxis
Rarely, a person experiences an allergic reaction to one or more of the ingredients in a vaccine. They might develop hives or another type of skin rash, swelling, and respiratory symptoms.
A severe allergic reaction is called anaphylaxis, and it involves low blood pressure, nausea, and difficulty breathing, among other symptoms.
Anaphylaxis is an extremely rare side effect of vaccination. According to the CDC, around 2–5 people per million, or fewer than 0.001% of people vaccinated in the U.S. have experienced anaphylaxis afterward.
Allergic reactions to mRNA vaccines have been of particular concern, as they contain a chemical, called polyethylene glycol (PEG), that has never been used in an approved vaccine before. PEG is in many drugs that have occasionally triggered anaphylaxis. In these vaccines, it coats the mRNA molecule and supports penetration into cells.
There are similar concerns about the Janssen vaccine, which contains polysorbate 80, a chemical that is structurally related to PEG.
A study of data about allergic reactions to mRNA COVID-19 vaccines noted that most people who experienced anaphylaxis afterward had a history of allergies and this particular severe reaction.
The data suggest that there is a very low risk of anaphylaxis as a result of mRNA COVID-19 vaccines. Regardless, the CDC recommend that vaccine administrators conduct prescreening for specific allergic reactions. These vaccines are safe for people with common allergies, such as to foods, pets, environmental elements, latex, and oral medications.
The CDC also recommend that anyone who has had an allergic reaction to one dose of a vaccine not receive a second dose of the same type of vaccine.
Frequency of side effects in women
Side effects appear to be more commonly reported in women than men. A study by CDC researchers shows that 78.7% of adverse event reports submitted during the first month of U.S. vaccination involved women.
Another study observed that females represented 15 out of 16 people with anaphylaxis after a vaccine.
These findings are in line with a 2013 study on the H1N1 vaccine during the 2009 flu pandemic, which found higher rates of hypersensitivity reactions among females of childbearing age than other groups in the study population.
Reproductive hormones, such as estrogen and testosterone, may play a role in this sex discrepancy. A study in mice suggests that estrogen causes the body to generate more antibodies, leading to a higher immune response.
Potential side effects per vaccine
Recently, there have been new concerns about serious side effects of COVID-19 vaccines.
These effects may be coincidental, and there is currently not enough conclusive evidence to link these effects to specific vaccines. However, regulatory agencies are taking precautionary measures to investigate these safety concerns.
Pfizer-BioNTech and Moderna
The Pfizer-BioNTech and Moderna vaccines are both two-dose mRNA vaccines. People have reported similar, common side effects after the second doses of each.
These COVID-19 vaccines are the first vaccines approved for use in humans that incorporate mRNA technology. As a result, there are concerns about the long-term effects and a risk of altering the body’s genetic information.
People may be unaware that researchers have spent many years studying the potential of mRNA vaccine technology. There have been efforts to develop mRNA vaccines in the past, including Moderna’s human-based trial of an mRNA Zika virus vaccine.
Furthermore, it is unlikely that an mRNA vaccine can alter genetic information. The mRNA in a vaccine does not enter the nucleus of a cell, where DNA is stored, and it degrades rather quickly in the body after it serves its purpose.
Yet many were alarmed by reports from Norway that 23 people had died shortly after receiving the Pfizer-BioNTech vaccine. However, there is no evidence that these deaths were a direct result of the vaccine.
“There is a possibility that these common adverse reactions — that are not dangerous in fitter, younger patients and are not unusual with vaccines —may aggravate underlying disease in the elderly,” suggests Dr. Steinar Madsen, the medical director of the Norwegian Medicines Agency.
“We are now asking for doctors to continue with the vaccination, but to carry out extra evaluation of very sick people whose underlying condition might be aggravated by it,” he adds.
Another death, which occurred in the U.S., was associated with having a low blood platelet count, or thrombocytopenia. So far, 20 thrombocytopenia cases have developed following either a Pfizer or Moderna vaccination. Currently, however, no causal evidence links these cases with the vaccines.
Other concerns involve pregnancy and fertility. According to a February 2021 statement from the American College of Obstetricians and Gynecologists, the American Society for Reproductive Medicine, and the Society for Maternal-Fetal Medicine:
“While fertility was not specifically studied in the clinical trials of the vaccine, no loss of fertility has been reported among trial participants or among the millions who have received the vaccines since their authorization, and no signs of infertility appeared in animal studies. Loss of fertility is scientifically unlikely.”
In a press statement later the same month, Pfizer and BioNTech announced that they have begun a COVID-19 vaccine clinical trial in 4,000 healthy pregnant women to explore the efficacy and safety for the participants and their babies. The results will hopefully provide further insight.
Janssen (Johnson & Johnson)
The Janssen vaccine can also cause common vaccine side effects.
The vaccine’s product information document provides details about precautions to take and the expected effects.
Oxford-AstraZeneca and Serum Institute of India
The European Medicines Agency (EMA) and Danish Health Authority recently observed that the Oxford-AstraZeneca vaccine has been followed by incidents of blood clots.
Of the 5 million people who received this vaccine, there have been 30 reported cases of blood clots. One case in Denmark was followed by death.
On March 18, 2021, the EMA concluded that the Oxford-AstraZeneca vaccine is safe and does not increase the overall risk of blood clots. They pointed out that the incidence rate of blood clots in people who have had the vaccine is lower than that in the general population.
The EMA did acknowledge extremely rare cases of thrombocytopenia, an issue that supports blood clot formation, following the vaccination. They are now incorporating this into their vaccine product information. Still, they highlight a lack of causal evidence and emphasize that the benefits of vaccination still outweigh the risks.
Multiple countries, including Denmark, Norway, Germany, and France, had paused the distribution of this vaccine as a precautionary response to the initial reports of blood clots. Many of these countries plan to resume the use of this vaccine, and there are concerns that this event has slowed down the timeline of vaccine distribution throughout Europe.
The Serum Institute of India’s Covishield is the locally manufactured version of the Oxford-AstraZeneca vaccine. India has not reported any incidents of blood clotting related to Covishield and currently has no plans to discontinue its distribution.
Drug regulatory agencies in India are still closely examining the data, however, to ensure that there are no causal links.
CanSino and Gamaleya
Both the CanSino and Gamaleya vaccines use the adenovirus type-5 (Ad5) as their delivery vehicle. The peer-reviewed research into trials of these vaccines found that they caused common side effects, none of which were serious.
However, a team that included Dr. Juliana McElrath, director of the Vaccine and Infectious Disease Division at the Fred Hutchinson Cancer Research Center, raised concerns about the use of Ad5 in COVID-19 vaccines.
A 2008 study found that the Ad5 HIV-1 vaccine was linked to increased susceptibility to HIV infection. Multiple follow-up studies found similar results to support this link.
The researchers recommend a cautious approach to Ad5-based COVID-19 vaccines, especially in areas most affected by the HIV and AIDS epidemic.
Published data from Bharat Biotech’s Covaxin phase 1 and 2 trials show no serious side effects. Otherwise, there is little information about the risk of adverse effects.
Sinopharm: Beijing and Wuhan
Sinopharm have manufactured two vaccines, developed with the Institute of Biological Products in Beijing and Wuhan, respectively.
The published phase 1 and 2 trial data for the BBIBP-CorV and inactivated Vero cell vaccines show that most of the adverse events were common side effects and that none were serious.
Phase 1 and 2 trial data for the CoronaVac vaccine indicate no reports of serious adverse events.
Interestingly, the study authors found fewer reports of fever among participants who received this vaccine, compared with those who had received the Pfizer-BioNTech, Oxford-AstraZeneca, or CanSino vaccines.
Anhui Zhifei Longcom
There is currently no publicly available peer-reviewed data about the safety or efficacy of the dimeric receptor-binding domain, or RBD-dimer, vaccine. One preprint paper states that no serious adverse events were reported during a trial.
EpiVacCorona is Russia’s second approved COVID-19 vaccine, and trials to determine its safety and efficacy are ongoing.
Tatyana Golikova, the country’s deputy prime minister, notes: “Unlike the first Russian vaccine, Sputnik V, which is a vector vaccine, that is, produced based on adenovirus, the new vaccine […] consists of artificially synthesized short fragments of viral proteins, peptides, through which the immune system learns and subsequently recognizes and neutralizes the virus.”