"Normally vaccines take years to develop. In the case of Covid-19, we developed them in a few months. They can't have been properly tested for safety in such a short time."

"Four people got Bell's Palsy after taking the Pfizer vaccine. This was caused by the vaccine."

"Reports from Norway in January 2021 indicate that 23 elderly people died shortly after having the Pfizer vaccine. This vaccine is not safe."

"What about long-term side effects? We simply haven't had enough time to test for these."

1) The speed of the trials hasn't compromised how much data has been collected on safety. It usually takes years or occasionally decades to approve a vaccine. There are several reasons why vaccines have been tested and approved so quickly for Covid-19, and they have not resulted in a compromise of safety.

Firstly, different phases of the trials have been run in parallel instead of sequentially, which would take far longer. This has been possible in part due to greater funding and collaboration. Secondly, the disease has been pervasive enough that participants have been recruited very rapidly, and a large number of people in the trials have caught the virus quickly, meaning scientists have been able to quickly find out whether vaccines would protect recipients in their trials, compared to those who received a placebo. Thirdly, for some vaccines, regulators have been investigating the data on vaccines while trials were ongoing instead of after they had completed, which has also saved time. In sum, vaccines have had to go through the same phases of trials, had the same data collected and had to pass the same standards as in usual times.

2. We have a huge amount of data from extensive testing of these vaccines. The Covid-19 vaccines which have been licensed for use in the UK have been through a very extensive testing process, involving tests on tens of thousands of people. As Oxford University's Vaccine Knowledge Project explains:

"The safety and efficacy of the [Pfizer] vaccine have been assessed in clinical trials of over 44,000 people in six countries: USA, Germany, Brazil, Argentina, South Africa and Turkey. The trial reported that the vaccine can prevent 95% of COVID-19 cases. This means that in a group of 20 people who are vaccinated, if all are exposed to the coronavirus, 19 people will be prevented from getting COVID-19. The trial also showed that the vaccine provides similar protection in people of all ages, races and ethnicities.

"The [AstraZeneca] vaccine has been tested by the University of Oxford in clinical trials of over 23,000 people in the UK, Brazil and South Africa. AstraZeneca are also running a further trial with 40,000 people in the USA, Argentina, Chile, Columbia and Peru.

"Interim results from the UK and Brazil trials showed that the vaccine can prevent 70.4% of COVID-19 cases. This was calculated across two different groups of people, who received two different dose regimens."

The clinical trials run to test these vaccines were thus extremely large - with so many participants, there are many opportunities to monitor for side effects.

Even before the final trials, the vaccines had been through an extensive testing process. The Oxford Vaccine Knowledge Project describes the many different stages of testing the vaccines have to go through before and after use. They are tested on individual cells, then non-human animals (usually mice), then increasingly large numbers of human participants. Even after the large clinical trials, the vaccines are monitored for safety and rare side effects. Any severe side effects were referred to the patient's doctor, as well as an independent safety committee.

As would be expected for any vaccine, minor side effects were common in both the Pfizer and AstraZeneca vaccines. These included arm pain around the injection site, fatigue, headache, and fever. These rarely lasted more than a few days.

2. Just because a medical condition occurred after a vaccine doesn't mean it caused it. Four people in the Pfizer trials were reported to have developed Bell's Palsy, a temporary facial paralysis. Remember, though, that the trial involved many thousands of people. As FullFact explains, we'd expect about four people from the total number to develop Bell's Palsy in any given year with or without a vaccine. So the association of the vaccine with the side effect doesn't mean anything - it's not necessarily evidence that the vaccine caused the side effect.

The same goes for any other medical condition that appears after a vaccine. Ask yourself: how likely was it that the person would have developed the condition anyway? Events with a probability of many thousands to one will occur quite a few times in studies of tens of thousands of participants.

3. Allergic reactions to vaccines are rare. In the US, the Centers for Disease Control and Prevention are recording reports of allergic reactions to the Pfizer and Moderna vaccines. In the first 1.8 million doses of Pfizer's vaccine that were administered, they detected 21 cases of anaphylaxis (a severe form of allergic reaction), which is a rate of 11.1 in a million. 71% of those reactions occurred in the first 15 minutes after people were vaccinated. Apart from anaphylaxis, they detected 83 cases of other allergic reactions, of which 87% were considered non-serious, resulting in symptoms such as rashes and itches.