The interval between two doses of Covid-19 vaccine
should follow the manufacturer's recommendations, if the second dose is slower
than recommended, it will not reduce the effectiveness of the vaccine.
Specifically, the interval between two doses of
AstraZeneca vaccine is at least 4 weeks, preferably 8-12 weeks. Two doses of
Moderna vaccine are given at least 4 weeks apart. The Pfizer vaccine is given
as two shots at least 3 weeks apart. Two doses of Sinopharm vaccine 3-4 weeks
apart.
According to the current guidelines of the Ministry of
Health, people who have received a single dose of a vaccine are best given the
second dose with the same type of vaccine. People who have been vaccinated with
Sinopharm, Pfizer, and Moderna vaccines are prescribed two injections of the
same type. In case of limited vaccine resources, if the first dose is
AstraZeneca vaccine, the second dose of Pfizer vaccine can be mixed. The
interval between two injections is 8-12 weeks.
Many people are worried that they will have to start
over again because of the time limit for the second dose of the vaccine. The
doctor said: "So far, there is no recommendation to start the vaccine
again and late injection does not reduce the effectiveness of the
vaccine."
The doctor explained, an intensive study conducted in
the UK on the gap between the two doses of the Pfizer vaccine produced an
antibody-producing immune response and a T-lymphocyte response. This is a very
important cell for the immune system. with long-term immunological memory and
helps generate antibodies.
The study was conducted on more than 500 healthcare
workers, assessing the level of antibodies and T-cell counts after two doses of
Pfizer vaccine with a short interval between two doses (3-4 weeks, average 24
days) and long (6-14 weeks, average 70 days).
The study results showed that, for the group with a
long injection interval, the antibody concentration decreased significantly
between the first and second dose. In particular, the concentration of
neutralizing antibodies against the Delta variant produced was worse after a
single dose and was not maintained in the period before the second dose.
However, T cells were well maintained between the first
and second doses. After two doses of the vaccine, neutralizing antibody levels
doubled. The longer interval between two shots of the vaccine leads to higher
levels of neutralizing antibodies after the second dose, helping the body fight
off the Delta variant and other variants.
"Regardless of the vaccination schedule, research shows that antibody and T-cell levels vary significantly from individual to individual. Outcomes depend on genetics, underlying health conditions and personal history. exposed to Covid-19 and other viruses," the doctor said.
There is currently no official recommendation from the
World Health Organization (WHO), the US Centers for Disease Control (CDC) or
the National Immunization Committees for one booster shot. after completing the
standard vaccination schedule with two doses of vaccine.
The protective effect of the vaccine is up to 6-12
months. In fact, those who are seriously ill hospitalized and die from Covid-19
are people who have not been vaccinated. In an effort to accelerate the
Covid-19 vaccination campaign and vaccine resources are limited, the vaccine is
still recommended according to the standard vaccination schedule. WHO will
consider considering the third dose of Covid-19 vaccine for groups of people
with weakened immune systems, including organ transplant recipients, people
being treated for cancer, leukemia, HIV-infected people, etc. .
People who have had two doses of the Covid-19 vaccine, depending on the country and local regulations, can participate in many of the activities you did before the pandemic. However, when herd immunity has not been achieved and to maximize the ability to protect the body from Delta variant as well as prevent the spread of the virus to others, we need to take measures to keep distance from people. as well as wearing a mask.
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