How Much Protection Does a Single Dose of Vaccine Offer?

How Much Protection Does a Single Dose of Vaccine Offer

You’ve probably heard about vaccines, but what do you really know about them? Are they safe? What do they do? And how much protection can you expect from one shot? Today, we’re going to talk about vaccine efficacy, which is the effectiveness of a particular vaccine in reducing the risk of contracting and spreading disease. To give you an idea of how much protection one shot of some popular vaccines offers, here are three helpful comparisons.


It may be a single shot, but it’s the ultimate fight against the flu: a one-time dose of influenza vaccine. A study in the journal Clinical Infectious Diseases estimates that about half of people aged 50 to 64 get protection from a single dose of a currently available influenza vaccine for at least six months. That drops to about 20% in those over 65. But does that mean you should need more than one shot for full protection? Not necessarily – researchers warn against assuming you need more than one dose when we’re still not sure what the best recommendations are for optimal protection levels.

Pneumococcal disease

Protection does a single dose of vaccine offer for Pneumococcal disease?

Infections with the bacteria can lead to pneumonia, which is a major cause of death in young children around the world. One in five globally still suffers from this disease, and an average of 20,000 children die every year from it. The three companies that produce the Pfizer pneumococcal vaccine have already donated or pledged more than 600 million doses to combat these diseases.

Ebola virus disease

When you get an Ebola vaccine, your body produces antibodies to help prevent you from getting sick. How much protection does a single dose of vaccine offer? There is no way to know for sure without gathering data about the rates of illness after vaccination. The earliest and largest study found that the protection is good for up to one year, but this result needs confirmation. Another study found that protection lasts between six months and a year, with better protection in women than in men or children. Further studies are planned to assess the duration of immunity and responses to booster doses


A single dose of rabies vaccine offers about 70-90% protection for people of any age who get the vaccine within 10 days of exposure. Some studies have shown that older people may need more than one dose to be protected from rabies. Other factors, such as how high the person’s risk is for getting rabies and how soon after exposure a person is vaccinated, can also affect their level of protection from the vaccine.

Varicella (chickenpox)

The Varicella vaccine, which is marketed as Varivax, reduces the risk of getting chickenpox by more than 90%. It is usually given to children, who need two doses. The first dose is usually given around age 12 months and the second shot around age 4-6 years.

Human papillomavirus (HPV), which causes cervical cancer

In the US, there are about 14,000 cases of cervical cancer each year. About 70% of these cases are caused by HPV. There are more than 100 different types (strains) of HPV and more than 30 strains that can infect the genitals. Two vaccines that have been shown to help prevent some types of HPV infection have been released in recent years: one from Pfizer and AstraZeneca, which is approved for girls aged 9-26; and one from Moderna, which is approved for men age 26-45.

The FDA has found the Pfizer vaccine has about 10 years of protection for the three doses recommended for most children or teens who start it before their 15th birthday.

Meningitis A

The single dose of Pfizer and AstraZeneca vaccines each provides coverage for 6 months, while Moderna’s vaccine offers protection for 12 months. MenB is a tougher disease to protect against, but the Pfizer and AstraZeneca vaccines offer 3 years of protection.


According to the Centers for Disease Control and Prevention, one dose of vaccine will protect against rotavirus in 60-90% of cases. However, this protection declines with each subsequent exposure to rotavirus. Therefore, the longer you are exposed to it, the less effective a single dose of vaccine becomes.

In addition, recent studies show that children vaccinated at two months old had lower levels of rotavirus immunity than those vaccinated at six months old.

Hepatitis B

We don’t know exactly how much protection a single dose of hepatitis B vaccine offers, but estimates range from 90% to 100%. The World Health Organization suggests that between 90% and 95% of people who have been vaccinated with the full course of three doses are protected.

Protection against hepatitis B is lifelong, so the vaccine is essential for people who are at risk for getting the virus.


The World Health Organization recommends that children in countries where measles is common should receive two doses of vaccine. A single dose provides 78% of the immunity against measles. The more people who are vaccinated, the less likely a person without immunity will be exposed to a measles virus and contract the disease. It takes about 21 days from exposure to show symptoms of measles so it is possible for a person to get infected before getting the second dose of vaccine if they were only vaccinated once. Getting vaccinated twice during infancy ensures that those with lowered immunity have greater protection against these diseases, even when they are not feeling well enough to get vaccinated again.

Leave a Reply

Your email address will not be published. Required fields are marked *