When you get a vaccine, your immune system response

What is vaccination?

Vaccination is a simple, safe, and effective way of protecting people against harmful diseases, before they come into contact with them. It uses your body’s natural defenses to build resistance to specific infections and makes your immune system stronger.

Vaccines train your immune system to create antibodies, just as it does when it’s exposed to a disease. However, because vaccines contain only killed or weakened forms of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complications.

Most vaccines are given by an injection, but some are given orally (by mouth) or sprayed into the nose.

Why is vaccination important?

Vaccination is a safe and effective way to prevent disease and save lives – now more than ever. Today there are vaccines available to protect against at least 20 diseases, such as diphtheria, tetanus, pertussis, influenza and measles. Together, these vaccines save the lives of up to 3 million people every year.

When we get vaccinated, we aren’t just protecting ourselves, but also those around us. Some people, like those who are seriously ill, are advised not to get certain vaccines – so they depend on the rest of us to get vaccinated and help reduce the spread of disease. 

During the COVID-19 pandemic, vaccination continues to be critically important. The pandemic has caused a decline in the number of children receiving routine immunizations, which could lead to an increase in illness and death from preventable diseases. WHO has urged countries to ensure that essential immunization and health services continue, despite the challenges posed by COVID-19.More information about the importance of vaccines is available.

Vaccines and immunization

Immunization is a global health and development success story, saving millions of lives every year. Vaccines reduce risks of getting a disease by working with your body’s natural defences to build protection. When you get a vaccine, your immune system responds.

We now have vaccines to prevent more than 20 life-threatening diseases, helping people of all ages live longer, healthier lives. Immunization currently prevents 2-3 million deaths every year from diseases like diphtheria, tetanus, pertussis, influenza and measles.

Immunization is a key component of primary health care and an indisputable human right. It’s also one of the best health investments money can buy. Vaccines are also critical to the prevention and control of infectious-disease outbreaks. They underpin global health security and will be a vital tool in the battle against antimicrobial resistance.

Yet despite tremendous progress, far too many people around the world – including nearly 20 million infants each year – have insufficient access to vaccines. In some countries, progress has stalled or even reversed, and there is a real risk that complacency will undermine past achievements.

Global vaccination coverage – the proportion of the world’s children who receive recommended vaccines – has remained the same over the past few years.

The research was led by Professor James Chalmers, a consultant respiratory physician from the University of Dundee, UK. He said: “We have always believed that front line health workers face a high risk of contracting COVID-19 and that’s why we’ve tried to ensure they have the PPE needed to protect themselves. But many questions remain about the level of this risk and what other measures we can take to protect staff and reduce transmission of the disease.” The study included a total of 2063 staff working in a wide variety of healthcare roles in in the East of Scotland. Between May and September 2020, participants were given blood tests for antibodies against COVID-19. The presence of these antibodies is a very accurate indication that someone has been infected with COVID-19. Researchers also recorded whether any participants developed an infection in the following months. Results from these healthcare workers were compared with a randomly selected control group of blood samples taken by local GPs during the same period of time.

The blood tests showed that 300 (14.5%) of the healthcare workers had been infected. This is more than three times higher than the proportion of people infected in the local population. The highest rates of infections among the workers were in dentistry (26%), health care assistants (23.3%) and hospital porters (22.2%). The rate among admin staff was the same as that of doctors (21.1%). Rates among people working in areas of the hospital where COVID-19 patients were being treated were a little higher than those working in non-COVID areas (17.4% compare to 13.5%). However, the majority of infections were in staff who were not working directly with COVID-19 patients, suggesting transmission between staff or infections acquired in the community.

Among the 300 healthcare workers who tested positive, 56 (18.7%) did not think they ever had COVID-19 and were completely asymptomatic. The researchers say this is important since people without symptoms are likely to go to work and could potentially infect other people.

Professor Anita Simonds, President of the European Respiratory Society and Consultant in Respiratory and Sleep Medicine at Royal Brompton Hospital, UK, was not involved in the research. She said: “This research shows the high levels of COVID-19 infection among all healthcare workers, with the highest evidence of infection in dentists, healthcare assistants and porters. Staff working in critical care, who are likely to have been protected by using personal protective equipment at all times, were not disproportionately affected.

Is there a vaccine for COVID-19?

 The first mass vaccination programme started in early December 2020 and the number of vaccination doses administered is updated on a daily basis. At least 13 different vaccines (across 4 platforms) have been administered.

The Pfizer/BioNtech Comirnaty vaccine was listed for WHO Emergency Use Listing (EUL) on 31 December 2020. The SII/Covishield and AstraZeneca/AZD1222 vaccines (developed by AstraZeneca/Oxford and manufactured by the State Institute of India and SK Bio respectively) were given EUL on 16 February. The Janssen/Ad26.COV 2.S developed by Johnson & Johnson, was listed for EUL on 12 March 2021. The Moderna COVID-19 vaccine (mRNA 1273) was listed for EUL on 30 April 2021 and the Sinopharm COVID-19 vaccine was listed for EUL on 7 May 2021. The Sinopharm vaccine is produced by Beijing Bio-Institute of Biological Products Co Ltd, subsidiary of China National Biotec Group (CNBG).

Once vaccines are demonstrated to be safe and efficacious, they must be authorized by national regulators, manufactured to exacting standards, and distributed. WHO is working with partners around the world to help coordinate key steps in this process, including to facilitate equitable access to safe and effective COVID-19 vaccines for the billions of people who will need them. More information about COVID-19 vaccine development is available.