Covid-19

How is the COVID-19 vaccine immune response affected by age?

A new study underlines the importance of COVID-19 vaccination in order to protect older vaccinated individuals. 

Age is a major factor that influences the mortality rates in COVID-19 infections as most of the deaths are seen in the elderly population, specifically those who are 60 and above. This higher mortality rate can be attributed to the lower titre of neutralising antibodies against the virus, overall loss of muscle structure and strength, and weakened physiology of several organs. Degenerative disorders such as diabetes, cardiovascular disorders, hypertension, and neurological issues present as comorbidities that can exacerbate a coronavirus infection in the older population. 

Aging is associated with several physiological and structural changes that occur in the body especially in the cardiovascular and pulmonary systems. Bones and muscles in the chest and spine become thinner, hence making it difficult for the lungs to expand and contract to full capacity. The diaphragm, a thick muscle found below the lungs that helps in breathing and bringing in more air to the respiratory system, also weakens while aging making it hard to breathe comfortably. 

Muscles and other tissues that line the airways may lose their ability to keep the airways completely open causing them to close and collapse easily. Aging also causes the air sacs to lose their shape and become baggy. These changes in lung tissue can allow air to get trapped in the lungs. A lesser amount of oxygen may enter the blood vessels and a lesser amount of carbon dioxide may be removed making it hard to breathe. 

The immune function also declines as you age. There is reduced production of B-cells and T-cells from the bone marrow in older individuals. The concentrations of immune chemicals such as cytokines are much lower thus not allowing for the proper functioning and maturation of various immune cells. Although the older population are not immunodeficient, their immune systems are unable to respond efficiently to novel or previously encountered antigens. 

Fikadu Tafesse and his colleagues from the Oregon Health and Science University found that older people appear to have fewer antibodies against the novel coronavirus. The study was published in the Journal of the American Medical Association. Patients over the age of 60 are a lot more susceptible to a severe SARS-CoV-2 infection even after vaccination. The elderly patients were found to have a lower titer of neutralising antibodies, than the younger patients. 

The scientists emphasize that the vaccines are still effective in preventing a coronavirus infection and severe illness in most people of all ages. They stated that vaccinations help to reduce the spread of the virus and protect the more susceptible older population from new and potentially more transmissible variants. Older people aren’t entirely safe just because they’re vaccinated; the people around them really need to be vaccinated as well. This study stresses on the necessity that everybody should be vaccinated in order to protect the community. 

The researchers measured the immune response in the blood of 50 people two weeks after their second dose of the Pfizer vaccine against COVID-19. They looked at the antibodies against the SARS-CoV-2 spike protein via the ELISA technique and focus reduction neutralisation tests. They then grouped participants into age groups and then exposed their blood serum in test tubes to the original “wild-type” SARS-CoV-2 virus and the P.1 variant (also known as gamma) that originated in Brazil.

The youngest group (almost all in their 20s) had a seven-fold increase in antibody response compared with the oldest group of people who were between 70 and 82 years of age. The laboratory results reflected a clear linear progression from youngest to oldest: The younger a participant, the more robust the antibody response.

The emerging SARS-CoV-2 variants of concern, including P.1, B.1.1.7, and B.1.351, have been widely reported to be less well-neutralized by vaccine-induced antibodies and were responsible for many of the fast-spreading infections seen during the second wave of the pandemic. The compounding effects of reduced neutralizing antibody titers due to both age and the variants of concern should be considered when designing policies around booster vaccinations.  

“The vaccines still produce strong immune responses compared with natural infection in most older individuals, even if they are lower than their younger counterparts. Vaccination in this group may make the difference between serious and mild disease, and likely reduces the chances of transmitting SARS-CoV-2 to another person,” state the scientists.

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