What is perhaps of most concern, amid the worrying coronavirus outbreak in Victoria, Australia, is that the virus has started to make its way into elderly care centers again. On Sunday, the state government announced that an elderly care worker, who received the first COVID vaccine vaccine on May 12, had tested positive for COVID-19 infection. After that, we learned that another staff member, who had worked with a COVID-positive member at Archare Maidstone, had tested positive with another resident.
The resident who tested positive for Kovid had taken the first dose of Pfizer vaccine and is reported to have mild symptoms of the disease, despite being monitored in hospital. The son of the worker who first tested positive was also found positive. The cases of the first worker and resident infected, both of whom received their first dose of vaccine, highlight the fact that you need both doses for maximum benefit. It takes a few weeks and tests show that protection against the COVID vaccine begins about two weeks after your second dose.
“The likelihood of symptoms of Kovid-19 is reduced”
This means that in healthy people who are almost completely protected from developing and dying from the severe form of COVID, the chances of having symptoms of COVID-19 are significantly reduced. Viruses reduce the risk of infection; even if you are infected, they reduce the amount of virus you produce. New evidence suggests that it also lowers your chances of passing the virus on to other people. Each dose of the vaccine essentially strengthens you against the disease.
Taking one dose of the vaccine makes you less likely to get some of these benefits, while taking two doses increases your chances of getting all of the benefits from the above vaccine. However, even after two doses, you can unfortunately become infected with the disease, experience its severe form, and pass the virus on to others. What do we know about a single dose of Pfizer? The Pfizer vaccine clinical trial was designed to test the efficacy of the vaccine more than a week after the second dose. However, these trials also initially indicated that the first dose may provide some protection against viral infection after day 12.
“Real-world” data now supports these early observations that the first dose four weeks after vaccination significantly reduces the risk of hospitalization. Meanwhile, early research and reports suggest that the first dose of Pfizer may be 50 to 90 percent effective in preventing infection. Preliminary data also suggests that people infected with SARS-CoV-2 after a single dose of Pfizer vaccine are up to 50% less likely to pass this infection on to other family members.
What about a single dose of AstraZeneca?
The AstraZeneca vaccine, originally developed as a single-dose vaccine, is estimated to be 76 percent effective against the disease in trials. These trials, subsequently modified to include a second dose, showed a significant increase in antibody levels in volunteers after the second dose. Real-world data has yet to be peer reviewed. He has shown that a single dose of a vaccine like Pfizer is about 65% effective in preventing infection and up to 50% effective in preventing transmission if those vaccinated become infected.
Similar to Pfizer, a single dose of AstraZeneca vaccine offers very good protection against hospitalization after four weeks. Why is it taking so long? Despite the difference between an mRNA vaccine like Pfizer and a viral vector vaccine like AstraZeneca, both take the same time to produce an antibody response. Antibodies can be detected for up to 14 days after a single dose of AstraZeneca and may increase over the next two weeks. But why do these reactions take so long to develop?
When researchers try to trace the antibody response to the first dose of the vaccine, they find that it takes at least ten days for the immune system to start making antibodies that bind to the SARS-CoV-2 spike protein. (the virus virus). a protein present on the surface that it uses to enter the cells of our body). T cells, which are a type of white blood cell important in our immune response, also take at least a week to start responding to the vaccine. These reactions become even stronger over the next few weeks. Conversely, the second dose activates the immune system more quickly.
Within a week of taking the second dose, your antibody levels increase tenfold, providing stronger and longer lasting protection against infections. So the first dose of the COVID vaccine maintains your immune response, but the second dose is needed to ensure that the immunity is strong and lasts longer. Partial immunization can be risky Although the first dose of any vaccine provides some benefit, the use of partial immunization can pose problems for people who are vulnerable or play a high-risk role.
All existing covid vaccines based on the original viral strain
It is important that we vaccinate front-line health workers, workers in quarantine centers and those caring for the elderly and disabled as soon as possible. Another challenge is that all current COVID vaccines are based on the original viral strain, but now many countries have all variants of the virus. Vaccines have little effect on some types, especially after a single dose. Preliminary data suggests that two doses of the Pfizer vaccine provide up to 88 percent protection against symptomatic B.1.617.2 variant infection, with an effective dose of only 33 percent. A variant of the virus causing the current outbreak in Victoria is similar to B.1.617.1 and may elicit a similar response.
It is therefore even more important to ensure that frontline workers receive their doses of both vaccines as quickly as possible. It should also be noted that the immune response to a single dose of Pfizer or AstraZeneca vaccines tends to decrease with age. In a joint analysis by Pfizer and AstraZeneca, older people had lower rates of protection than younger people after a single dose, although the protection of older people after two doses was similar to younger people. Although this study has not yet been reviewed, it teaches us that it is especially important to give older people a second dose of the vaccine on time, so that they can fully benefit from the vaccination.
Kylie Quinn, RMIT University and Jennifer Juno, The Peter Doherty Institute for Infection and Immunity