One surest way experts say can help curb the spread of Coronavirus is through vaccination. Vaccination prevents the spread of the virus by making one immune to it.
But does immunity last forever?
Does one’s status revert to its original state weeks, months, or years after taking the vaccination? In this report, Fact-Check Ghana reviews what experts say.
What is Immunity?
According to the Merriam-Webster dictionary, Immunity is a condition of being able to resist a particular disease especially through preventing the development of a pathogenic microorganism or by counteracting the effects of its products. In simple terms, Immunity is the state of protection from an infectious disease.
How does one attain Immunity?
Immunity to a disease is achieved through the presence of antibodies to that disease in a person’s system. Antibodies are proteins produced by the body to neutralise or destroy toxins or disease-carrying organisms. Antibodies are disease-specific. For example, a measles antibody will protect a person who is exposed to measles disease, but cannot protect that person from yellow fever. There are two basic means of attaining immunity for any form of disease or virus –Active and Passive Immunity.
Active Immunity is attained when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Exposure to the disease organism can occur through infection with the actual disease (resulting in natural immunity), or introduction of a killed or weakened form of the disease organism through vaccination (vaccine-induced immunity).
Either way, if an immune person comes into contact with that disease in the future, their immune system will recognise it and immediately produce the antibodies needed to fight it. Active immunity is long-lasting, and sometimes life-long.
Passive Immunity, on the other hand, is provided when a person is given antibodies to a disease rather than producing them through his or her immune system. A newborn baby acquires passive immunity from its mother through the placenta. A person can also get passive immunity through antibody-containing blood products such as immune globulin, which may be given when immediate protection from a specific disease is needed.
How long does it take to build immunity to a disease?
According to experts, it normally takes a few days and weeks for one’s body to manufacture antibodies or organisms that fight a disease. It takes the same amount of time whether one gets a vaccine or has an illness.
One can also get the disease if he comes into contact with it within the period after taking a vaccine, but before enough antibodies are produced to fight the disease especially in the case of active immunity.
How long does Immunity from a disease last after one gets the disease or vaccinated?
Usually, the duration for Immunity differs from disease to disease and person to person. The immune system of a person, depending on how strong it is can elongate how that system can fight a particular disease whereas one with an underlining health condition may have a shorter duration of fighting a disease.
Therefore, the length of time one for immunity against a disease varies. Some vaccines give immunity for a lifetime after two or three doses, whilst other vaccines such as the influenza vaccine, require annual doses called “boosters” to continue the protection.
How long does vaccine Immunity last?
After a person acquires a virus, the immune system retains a memory of it. According to the National Institutes of Health (NIH), a medical research agency of the U.S. Department of Health and Human Services, “Immune cells and proteins that circulate in the body can recognise and kill the pathogen if it’s encountered again, protecting against disease and reducing illness severity.”
According to the Institute, there are four components of immunity protection :
- Antibodies – proteins that circulate in the blood and recognise foreign substances like viruses and neutralise them.
- Helper T cells – help to recognise pathogens.
- Killer T cells – kill the pathogens.
- B cells – make new antibodies when the body needs them.
People who recover from COVID-19 have been found to have all four of these components. However, specifics about what this means for the immune response and how long immunity lasts are not clear.
A recent study published in the journal Science has found that immunity can last for as long as 8 months. According to Shane Crotty, Ph.D., a professor at the La Jolla Institute for Immunology in California, who co-led a study into the duration of immunity from COVID-19, his team measured all four components of immune memory in almost 200 people who had been exposed to SARS-CoV-2, which causes the COVID-19, and recovered.
The researchers found that the four factors persisted for at least 8 months following infection with the virus. This is important because this shows that the body can “remember” SARS-CoV-2. If it encounters the virus again, the memory B cells can quickly gear up and produce antibodies to fight it. Those who have recovered from COVID-19 could have immunity for months or perhaps even years, the authors said.
In a different study published in The New England Journal of Medicine, researchers in Iceland studied 1,107 people who had recovered from COVID-19 and tested positive for the antibodies. The results indicate that antiviral antibodies against SARS-CoV-2 did not decline within 4 months after diagnosis.
The Washington Post also states that even though health authorities have not provided a definitive answer to the question about duration, based on clinical trials, experts do know that vaccine-induced protection should last a minimum of about three months.
In the real world, the protection should last quite a bit longer, though the length of time still needs to be determined with further studies, experts say. Certain factors may influence how much protection they provide and for how long.
Chunhuei Chi, Director of the Center for Global Health at Oregon State University, said immune responses vary from person to person. People who have a stronger immune response to a vaccine will produce more antibodies and memory cells — and therefore have stronger immunity, he said. But there is no evidence currently to show that a stronger immune response will increase the duration of immunity.
How long does COVID-19 vaccine Immunity last?
On April 1, Pfizer announced that its vaccine offers up to six months of strong protection against symptomatic COVID-19. Specifically, data from its phase 3 trial showed that the vaccine was 91.3% effective at preventing COVID-19 for up to six months after the second dose and 100% effective against severe disease as defined by the Centre for Disease Control and Prevention (CDC).
Moderna’s vaccine offers similar protection so far, according to a letter published in The New England Journal of Medicine on 6th April. Researchers found that “antibody activity remained high” through six months after the second dose in all age groups.
Richard Watkins, M.D., an infectious disease specialist and professor of internal medicine at the Northeast Ohio Medical University, says they have similar results because these vaccines both use mRNA technology, and therefore elicit an immune response in the same way.
At this point, “six months is the time frame for which they have secure information,” explains William Schaffner, M.D., an infectious disease specialist, and professor at the Vanderbilt University School of Medicine.
But that doesn’t mean that the vaccines are only good for six months. It’s likely that the Pfizer and Moderna vaccines, and others like them, will provide immunity for longer than that, says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. He bases his prediction on experience with the flu vaccine, which is good for at least a year.
For the Johnson & Johnson’s vaccine, there are fewer data to work with as the U.S Food and Drug Administration’s authorisation came only two months after the mRNA vaccines. This single-dose vaccine uses a different method of action—it’s a traditional adenovirus vaccine, like the flu vaccine but it should also offer similar immunity, notes Dr Schaffner. This is because “the outcome of the antibodies to SARS-CoV-2 is the same with both types of vaccines,” he says.
However, a study of around 2,000 people suggests that, while the Oxford-AstraZeneca vaccine may offer more limited protection against mild and moderate disease caused by the South Africa variant, it should still protect against severe disease.
In conclusion, even though some COVID-19 vaccines provide immunity for a minimum period of at least three months, some can also protect up to a maximum of eight months when the full shots are taken. However, research suggests the duration could span from months to years as the novel nature of the pandemic gives room for more discoveries to be made about the virus.
This report is produced under the project: COVID-19 Response in Africa: Together for Reliable Information being implemented with funding support from the European Union.